Top Ten Activities that can Help you Learn about Physics

Activity Number 1: Sky Dive 
     The physics concept that sky diving can teach you the most about is called projectile motion. Projectile motion is the affect on an object that has both air resistance and horizontal factors that change the motion of the object. The formula you need to know to find your horizontal velocity is velocity equals distance over time (v=d/t). This formula can also be used to find the distance and the time (horizontally only) of your fall. Horizontal velocity, unlike vertical velocity, stays constant the entire time that you are falling through the air. When it comes to vertical velocity, you will gain 9.8 meters squared each second you are going down and loose that much each second you are going up. The second you jump out of a plane to sky dive, you start gaining velocity. You keep gaining velocity until you reach something called terminal velocity. Terminal velocity is a state where your weight is equal to the air resistance acting on you, so your velocity will stay the same until something changes your weight or your air resistance. You can also learn about acceleration while sky diving. Once you jump out of the plane, you will first accelerate and then the acceleration will decrease until it is at zero when you are falling with terminal velocity. Once you are at terminal velocity, you deploy your parachute because the two things that affect air resistance are surface area and speed. The parachute adds surface area to you which adds air resistance, and causes you to slow down until you have reached a new terminal velocity. The acceleration is decelerating during this change. This is not the only way to learn about projectile motion, but it would definitely be the best field trip to take.
Activity Number 2: Spend money with a credit card
      This activity is probably one of the weirdest ways you can learn about physics, however, it is also the most common. Every credit card is embedded with a series of magnet. Every credit card machine has loops of wire surrounding the area used to swipe the card. Each time a card is swiped, the magnetic field of the magnets inside the credit card alter the magnetic field of the loops of wire inside the machine. This alteration causes a voltage to be induced into the wire which causes a current. This process is a physics concept called electromagnetic induction.
Activity Number 3: Carry a backpack up the stairs
     It's surprising to think that we use physics concepts every day of our lives, but, we do. When you carry your back pack around, you are doing a physics concept called work. Work is the ability an object has to do something. The equation for work is work equals distance times time. The thing you must know about work in order to understand when you are doing work on your back pack is that in order for work to be done force and distance must be parallel. This means, that because your backpack has a force down and you are forcing it up, you are doing work on it when you walk up the stairs. However, when you walk down a straight hall way, your back pack's force is still down but your distance is now perpendicular to the force. This means that you aren't doing any work on the back pack.
Activity Number 4: Go to a Wrestling Match
    In almost every sport at least one or more physics concepts can be applied. In wrestling,  center of gravity and base of support can all help the wrestlers with their strategy to win. Center of gravity is the point on the object that holds it up and is normally right above and in the center of the base of support. The center of gravity for people is our hips. So, if the wrestlers lower their hips, they can move their center of gravity closer to the base of support. This simple move causes them to be much more stable, and therefore be tackled less.
Activity Number 5: Go to a Roller Derby
    In roller derby there is a move called the sling shot. This is when one player holds the other players foot or hand in their hand and then they pull the player around them and shoot them forward. This helps them win because of a physics concept called tangential velocity. The girl that is shot forward gains speed because she is farther away from the center of the "circle" that the girl can create with her arm. Because she is farther away, she needs to go twice as fast as someone who would be right next to the girl who shot her forward because the girl right next to her would not have to move as fast to go one rotation. So, the girl is shot forward at a speed much greater then the girl who pulled her forward or the girls who are just skating regularly, and that team wins.
Activity Number 6: Fly in a Circle on an Airplane
     Have you ever wondered why tilting a plane makes it go in a circle? Well, that is because of a physics concept called centripetal motion. This is because when you draw the vectors of both the support force and weight (or force of gravity) of a plane, you get a line that is pointed inwards and down, and that is what is called the centripetal motion. Here is a picture to help you better understand:

Activity Number 7: Go to a Baseball Game
     A baseball game can help you learn about one of Newton's 3 major laws, Newton's second law. This law states that acceleration is directly proportional to force and inversely proportional to mass. Baseball can help you learn about this because is it so helpful to understand this law by applying it to hitting a baseball. The harder you hit the baseball, the higher the acceleration will be because acceleration is directly proportional to force. The lighter base ball you have, the more the baseball will accelerate because acceleration is inversely proportional to mass.
Activity Number 8: Learn how to Ice Skate
     In partner ice skating, there is a move when the guy throws the girl up into the air and she spins and then lands. It is probably one of the most challenging moves in partner figure skating, but it is also one of the coolest. The reason that this is possible is because of the physics concepts called rotational inertia and angular momentum. When an object has high rotational inertia it means that most of its weight is away from its axis meaning it is difficult for that object to spin. When it has low angular momentum, however, it means that most of its weight is near the center of the axis, making it much easier for the object to turn. In order to do this ice skating move, the woman must have very low angular momentum. This is why she pulls her arms into her chest as tight as she possibly can as soon as she is thrown into the air. Angular momentum is when there are as few sharp angles on an object as possible so that it will be easier to turn. This is another reason why she pulls her arms so tight into her chest and lays them as flat as possible. Here is an example.

Activity Number 9: Go to the Ocean and Watch the Tides
     The physics concept that can teach us the most about tides is the universal gravitational formula. This formula is force equals gravity times mass one times mass two all divided by the distance between the two masses squared. Gravity in this formula should always equal 7 times ten to the negative 11. When the moon is on the left side of the earth, the distance to the right side of the earth is very large, therefore the force on the ocean on the left side of the earth is very small. This is because force and distance are inversely proportional in the universal gravitational formula. The moon is not always in the same place so there are two different types of tides. When the moon is either on the right or left side of the earth the tides are called spring tides. Spring tides are when there is a full or new moon, and the tides are average meaning not high or low. When the moon is either above or below the earth the tides are called neap tides. These tides are higher or lower than normal tides because of the distance to ocean is from the moon. Because the moon has a cycle of twenty seven days, the tides are different each months, so you can not predict them.
Activity Number 10: Ride a Hovercraft 
     Riding a hovercraft helps to learn about Newton's first law of inertia. The law of inertia states that an object in motion will stay in motion and an object at rest will stay at rest unless acted upon by an outside force. A hovercraft riding on a hovercraft you can experience this law because if another person pushes you a lot then you will glide at the same rate until someone else stops you or until you hit a wall. A hovercraft also helps to learn about acceleration because seeing different sized people being pushed you can see that mass and force affect acceleration. This is because the heavier people need to have a much bigger push to go the same speed as a smaller person.

Unit 7 Reflection

 In this unit I have learned about charges, magnetic fields, electric fields, magnetism, magnetic poles, electromagnetic induction, generators, transformers, and how motors work. 

   The most important thing you need to know about charges is that the main source of magnetism is moving charges. All charges have electric fields in them, but only moving charges have both magnetic and electric fields. All objects have something called a domain. A magnetic domain is the direction in which the electrons in a magnetic field are going. When the electrons are all going in different directions, the object that contains the magnetic field is not magnetized. When they are all going in the same direction, however, there are poles which means that the object is magnetized. Magnetic fields flow from south to north. This means, that inside the magnet, the electrons flow upwards. Outside of the magnet, however, the magnetic field lines are the opposite. They flow from north to south. 

     The magnetic field of the earth is the opposite of what you think it is. We call the pole near antarctica the south pole and the pole where "santa claus" supposedly lives the north pole. It is true, these are the correct names of the magnetic field lines. However, the actual "magnet" that is inside the earth has the north pole at Antarctica and the south pole near santa claus. The reason that this is the way it is is because we only feel the force of the magnetic field lines around the magnet, not the magnet field inside the magnet itself. 

     Have you ever stuck a paper clip to a magnet, and wondered why it sticked? Paper clips are not magnetic, however, there is a way to magnetize them. A paperclips electrons are all flowing in different directions. The magnetic field of a magnet, however, pulls the magnetic domain of the paper clip towards its north pole when the paper clip is touched to the magnet. Because the magnets and the paper clips domain are in the same direction, the electrons are all flowing north. Therefore, the paper clip sticks and becomes magnetized. 

     When a charged particle is perpendicular to a magnetic field, the field repels it with maximum force. When a charged particle is parallel to a magnetic field, however, the particle joins the field without feeling a force. The easiest way to think about this is to think about the earths magnetic field and cosmic rays. Most everyone knows that the people who live on the poles are more susceptible to diseases caused by contact with cosmic rays. This is because the particles are parallel with the magnetic fields at these poles, and therefore feel no force (meaning have no trouble) entering the magnetic field of the earth.

      Electromagnetic induction is simply the process of putting a magnet through or around a series of loops of wire to generate a current or induce a voltage. The way that it works is, when you move a magnet over a wire, it changes the magnetic fields of the loops of wire and this change induces a voltage which causes a current. Believe it or not, this concept is used in our everyday lives. A car is a magnet, and the pavement has wires underneath, and this is how stop lights know if a car is waiting. Your credit card has magnets, and the machine has wires, and that is how stores know what your credit card number is. 

    Generators use electromagnetic induction to induce a voltage and create a current. They use mechanical energy in and get electrical energy out. This is because they simply have to crank something which moves magnets over a coil of wires and this movement causes a change in the magnetic field which causes a current.

     Motors are the opposite of generators, because you put electrical energy in and get mechanical energy out. We made a motor in class. We did this by using the concept of a motor and applying it to a battery, a coil of wire, two paper clips, a magnet, and two rubber bands. We did this by first bending the paper clips to make them capbaple of holding the coil of wire above both the batter and the magnet, and touching both sides of the batter in order to be able to carry the current to the wire. Then we wrapped rubber bands around the battery so that the paper clips would stay. Next, we put the magnet on the battery on the top in the middle. After that, we did the most important part. We wrapped the wire into an ovular coil that had about one inch of extra wire on each side. Then, we scraped the top (and only the top) of both wires. The scraping part is probably the most important part of the whole motor. This is because when the wire is carrying current, the magnetic field of the wire changes because of the magnet, and the electrons in the wire feel a force. The force is the greatest force possible because the coil of wire is perpendicular to the magnetic field of the magnet. This force causes a torque, which causes the coil to spin. Because the wire does not get current at all sides, and only on top, this happens over and over again. Then, you can attach a fan blade, the blade of a blender, or even wheels. This is how all motors work. Seems pretty simple, doesn’t it?

     The next and last thing we learned about was probably also the most complicated. It is a thing called transformers, and like all the other things we have learned about in this unit, it is used in our everyday lives. Transformers are simply a large coil of wires and a small coil of wires that, depending on which size is first, can either increase or decrease the voltage given to an appliance or a house. Transformers can also be used for computers, cell phone charges and many other appliances. Transformers use alternating current in order to change the voltage in the ways needed. They would not work with direct current. There are many transformers in the power lines to our houses. They have high voltage so that when they give power to our house, it is easier to reduce the voltage and increase the current. The way you figure out how many loops or volts are in the primary or secondary coil of wires is through the equation primary # of loops/primary voltage= secondary # of loops/secondary voltage.
     What I have found difficult about what we have studied is all the different points you have to make when answering each question. I overcame these difficulties by practicing answering each question a lot of times and thinking about the different concepts in relation to each other. My problem-solving skills and effort this unit have been pretty good over all. I have done all my homework and tried to study for each quiz that we had. I think my groups podcast this unit was one of our bet and we all collaborated really well with each other. My goals for the net unit is to try to rely less on what we learn in class and I plan to achieve this by paying more attention to the reading.
     I can make tons of connections to the real world from this unit because everything we studied can be connected to our everyday lives. Credit cards, car motors, security at airports, and even stop lights can all be connected back to these physics concepts. 

My Mini Motor

We created a motor in class using only a long piece of copper wire, a battery, two paper clips, and a magnet. In order to understand how it works, you must first know the function of each part of this motor. The battery was used because it supplies current, the coil of wire was used in order to carry the current, the paperclips were used to support the coil and carry the current, and the magnet was used to pull the wire coil.
     The first thing you need to do is attach the magnet to the battery and bend the paperclips in a way to hold the wire. Then you attach the paperclips to each end of the battery and tie a rubber band around it so that they stay attached. Then you take the long coil of wire and wrap it in an oval, making sure that the sides are parallel and that it is tightly wrapped. You also have to leave about an inch on each side so that the paperclips can hold the coil up. In order for the motor to actually be able to power something, you must take a sharp razor and scrape the wire until you see the silver part. A very key part of this is that you can not  scrape more than one side of the wire. If the motor is scraped all the way around, it will not work. Therefore you can only scrape the wire in one place on both sides. I will explain why later.
     The reason that this motor works is because of the magnetic field created by the current through the wire and the magnet. The magnet is facing up which means that the magnetic field it creates is running from north to south outside the magnet. The wire is perpendicular to this magnetic field, therefore when there is current through the wire there is a maximum force applied to the wire. Because the wire is attracted to this downward force, it is pulled in a direction that is towards the magnet. If you had scraped the entire circumference of the wire, the wire would constantly have a current going through it and therefore stay in a position where it is being pulled towards the wire. However, because you only scraped one part of the wire, the coil is pulled towards the magnet while it has current through it. This creates a torque. Then, once the part that you scraped is no longer touching the paperclips, the force and torque of the current being perpendicular to the magnetic field causes the coil to be pulled all the way back around. Then, the process repeats. Now, you have a motor!!
There are many things you can do now to use this motor. You could attached a small fan, the blades on a blender, and even a small motor cars wheel's! Really anything that spins that needs energy in order to move and be used now, and that's how motors work!

Magnetism Recourse

This video combines two different things that we have learned about; magnetism and induction. Using the example of a flashlight that works without batteries, it explains how you can create enough of a current using only a magnet and a wire to power this flashlight. You do this by shaking the magnet up and down, so that the electrons in the wire create a current that powers the bulb.

Unit 6 Pic

We learned about a lot of different things that can relate to this lightbulb. First of all, the light is off. When you turn the switch on the back, the circuit closes and tells the electrons inside the wire to start moving, creating current. The type of current that runs through this lightbulb is alternating current, which means the electrons are moving back and forth to create current. In order to prevent a fire from the energy that is converted to heat in the wires and not used in the filament of the lightbulb, there is a fuse right behind the plug where I plugged this light in. That fuse is a glass tube with a small metal bar through the center. When the wire gets too hot, the wire inside the glass tube breaks which breaks the circuit, even if the light's switch is on.

Unit 6

This unit was all about electricity. We learned about current, resistance, voltage, charge, electric fields and shielding, polarization, circuit breakers, parallel circuits, series circuits, and fuses.
    Current is measured in amperes, and can only be created if there is a difference in voltage. For example, if one side of a power unit had 70 volts of power and the other also had 70 volts, there would be no current therefore no power. This is because electrons flow from high voltage to low voltage. Voltage is measured in volts and is equal to the potential energy over the charge. When the wires conducting the current are wide and short the current flows more quickly and when the wires are thin and long the current flows more slowly. There are two different kinds of current, alternating current and direct current. All houses now a days are wired with alternating current, and only very few things (one of them being batteries) are wired with direct current. Alternating current is when the electrons in a wire move back and fourth all together to create a current. Direct current is when the electrons flow in a circle to create current. Alternating current is more popular because it is less dangerous and more efficient.
     Resistance is measured in Ohms. Resistance is used in order to lower the brightness on a light bulb or to give a device a smaller current than is using from the wall. Ohms law says that resistance is inversely proportional to current and directly proportional to voltage. Ohms law is current equals voltage over resistance, or , I(current)=V(Voltage)/R(resistance).
    Voltage, as I said earlier, is equal to the electrical potential over the charge. Difference in voltage is the only thing that can create electrical current. When a device has a large difference in voltage and you touch the wires in a way that causes the energy to go through you, you could get very hurt because a high number of electrons are flowing through your body. When you stand on a insulator, however, like a wooden chair or a carpet, it does not allow the energy to flow to the ground therefore you can not be hurt.
    There are two different types of charges, positive and negative. Positive charges have more protons than electrons and negative charges have more electrons than protons. There are three different types of ways for something neutral can be charged. Contact, friction, and induction. Contact and friction are cause by an object stealing electrons or protons from another object in order to become charged. Induction is a way to charge without contact. The reason that your hair sticks up when you take off your sweater is because your hair and the sweater rub against each other creating friction. This friction causes your hair to become positively charged and the sweater to become negatively charged. Because like charges repel each other, the protons in your hair are repelling each other causing your hair to stand up.
    Electric fields and shielding was the hardest part of the unit for me to learn. However, once I got the hang of it it became very easy. An electric field is the area around a charge that can influence another charge. Every electronic is put in a metal case because  all of the circuit boards on objects such as vcrs, play stations, phones, even ipods have an electric field around it that, if touched by another charge, could ruin the electronic for good. Metal is not a conductor, therefore the electric field inside the metal case can not be harmed and the object will never be ruined because of another charge.
    Polarization explains why plastic wrap sticks to glass bowls and why balloons stick to walls when you rub them against your head. There are two types of objects, conductors and insulators. Conductors let charges move through them, insulators stop charges from moving. Conductors are the only types of objects that can become polar. Since glass is a conductor, the friction from the plastic wrap being torn from the box causes the wrap to become charged. Since the bowl is neutral, when the wrap touches the glass it causes the like charges to repel to the other side of the bowl and the opposite charges to be attracted to the top of the bowl. According to coulombs law, which states that the force between any 2 charges is inversely proportional to the distance, the force between the top of the bowl and the wrap is greater than the force between the bottom of the bowl and the wrap, therefore it sticks. The formula for coulombs law is f(force)=q1q2(q=charge)/d^2(distance squared). An easy way to understand coulombs law is to look at it like this;
the smaller the force the bigger the distance df
and the larger the force the smaller the distance df
    Circuit breakers and fuses are used for the same purpose. The energy that voltage creates is not all used up by the device, some of it is converted to heat. The higher the current, the more heat you have. If you have too much heat you have a fire and your house burns down, and no one wants that. So, circuit breakers and fuses both make a closed circuit open when it gets to hot, but they do it in different ways. A fuse is what we learned about most, because it is what is most used. A fuse is a small metal wire inside of a glass tube that is connected to either the positive or negative side of the power source. It is placed there so that when the wire gets too hot, the metal inside the glass melts and breaks the circuit of the whole house, not just one object, therefore preventing fires throughout the whole house.
    There are two different types of circuits. Parallel circuits and series circuits. Series circuits are when every device is connected together and to one power source. In a series circuit the more devices you add the smaller the current gets and the less energy the devices in the circuit are allowed to use up. In a parallel circuit, each device completes its own circuit with the power source. So, the more devices you add the higher the current needs to be to supply each device with the right amount of power. Houses are wired in parallel, and almost nothing is wired in series.
    I found electric shielding and fuses the most difficult to learn because there is so much to remember. However, I overcame these difficulties by visualizing how they work and looking at many different kinds of examples of each in order to get the best understanding that I could.
     My problem solving skills and effort in this unit have not been as top notch as others, however I got all my homework and studied for all the quizzes and the test. I was as creative as I could of been, but my self-confidence in physics was lower than usual which made me realize that I could have definitely used more time to go over everything we had learned since it was such a big unit.
    It is very easy to make connections to the real world with this unit simply because we use tons of electricity everyday. Now I know why my computer and phone are in metal cases. I know why lights burn out when you turn them on, how my house is powered, where the electricity I use to plug in my curling iron comes from, and many other things.

Mousetrap Race Car Challenge

Our car came in second place and went five meters in 4.75 seconds.

Building our mousetrap race car was very challenging, but the hardest part was determining the ways in which so many different physics concepts could apply to one thing. All three of Newton's laws applied. The first, newton's law of inertia, applied because all we had to do was find a way to set the object the object in motion. This is because the law of inertia states that an object in motion will stay in motion unless acted upon by an outside force. We knew there was already an outside force that would be acting on the object, that was friction, therefore we also knew that we needed to set the object in motion long enough for the car to roll 5 meters without the car stopping. Newton's second law, the law that states that acceleration is directly proportional to force and inversely proportional to mass. So we knew we had to make the car as light as possible and the force that set it in motion as strong as possible for maximum acceleration. Newtons third law, the law that every action has an equal and opposite reaction easily applied because it also showed us that we needed to have a big force when the mousetrap closed in order to move the car a full five meters. All three of these things helped a lot in the initial thinking about how we were going to design our car. 

Friction played a huge part in building our car. One problem was that the less friction then the longer the object would stay in motion without being stopped by the friction. Another problem was that the more friction we had the more grip it would have on the ground to roll quickly. Since we needed both distance and speed, we put friction only in the back by wrapping balloons around the edges and no friction on the front wheels so that the car would roll with some force but be basically frictionless in the front. We had to take friction into account when looking at how to get as little friction as possible between the wheel and the body of the car and the friction of the wheels and the ground. 

We had to take many factors in when deciding how many wheels to use and what sizes we would make the front and back wheels. We had to look at rotational inertia, rotational velocity, and tangential velocity into account. We knew that the car would balance the best on four wheels and that that would be most effective when it came to turning the axle, so that's what we went with. We had trouble deciding between small wheels in the front and big wheels in the back or the same size wheels on every side of the axle, but we knew that the car would go more straight and therefore cover less amount of distance if all the wheels were the same size. We also knew that the bigger the wheels were the bigger tangential velocity they had and we wanted as big of velocity as possible so we went with four big wheels. 

The conservation of energy law says that no energy is every lost or destroyed it is simply converted. This is proven when it comes to our car because when the mouse trap is set there is an large amount of potential energy due to tension between the metal bar and the lever arm and the string that is attached to the end of the lever arm. When the mousetrap is released, the potential energy begins to convert to kinetic energy as the car does work and moves forward. 

The length of our lever arm was about 5 inches long. We attached two 5 inch long wires (from a wirer hanger) to the sides of the part of the mousetrap that needs to be pulled back in order to be set and hot glued and taped them on to make them secure. At first we had a very long lever arm that was only on one side of the part of the mousetrap, however that did not work. In fact, the shorter we made our lever arm, after we added one to the other side, the longer it went because the faster it was able to pull the string forward and therefore the wheel. This is because the shorter it was the more pulling force it was able to have. The more force, the faster it went. Since the work is always the same shortening the lever arm shortened the time and therefore increasing the power produced. 

Rotational inertia, rotational velocity, and tangential velocity all played parts in the functioning of my car when it came to the wheels. The more weight we had at the center of the wheels, the less rotational inertia and therefore the more likely it was to spin. Thats why we put tap, which is relatively heavy, and super glued the wheels to the tape to add weight. The rotational velocity of the wheels was all the same because we had the same sized wheels. The tangential velocity of the wheels was greater than it would have been if we had used two small wheels and two big wheels because instead we just used two big wheels and the farther away it is from the center the faster it goes. All of these things helped to improve the speed of our car. 

The reason that we are not able to calculate the amount of work the spring does on the car is because the force applied and the distance it goes are not parallel, and when the force and the distance are not parallel no work is done. The reason we can't calculate the amount of potential energy that was stored in the spring is because not only do we not know its mass but we also do not know its height. The reason we can't calculate the kinetic energy is because we do not know the velocity of the car. We can not calculate the force the spring exerted on the car to accelerate it because there was a lever arm and also we don't know the mass of the spring or the speed of the car so we can not calculate how much it was accelerated. 

 

Reflection

     Our final design was completely different from our original design. What promoted these changes was mainly that we changed the car in order to make it travel the full 5 meters. We stabilized the wheels, made the wheels have less friction by removing tape and adding balloons to the back wheels, and shorted the lever arm to increase the force that pulled the string. The majors problems that we encountered in the performance of our car was that for a while it would only travel about half of the 5 meters. The lever arm was way to long at first and we didn't understand why it wasn't working. It took a lot of patience and researching what was the problem with our car. 

    If we were to do this project again, I would first not have my mousetrap glued to anything and instead just have made the mousetrap the main body of the car. I also would have done what the group with the fastest car did and not have a lever arm to save time and supplies. 

Unit 5 Reflection

In this unit the first thing I learned about was work. Work is the ability an object has to do something and the equation for work is force times distance. The most important thing I learned about work is that the force and distance must be parallel, otherwise there is no work being done. The units for watts are joules and since work never changes the bigger the distance the smaller the force or the bigger the force the smaller the distance. For example,

w=df
w=df
The second thing I learned about was power. The formula for power is work over time. The units for power are watts which one watt equals one joule over one second. Power measures energy. Cars are measured in horse power, and one horse power is equal to 746 watts. Therefore, it is possible to create a horsepower if you can create 746 watts of power.
The third thing I learned about was kinetic energy. Kinetic energy is the amount of energy an object is using and is directly related to not only work but potential energy. The kinetic energy of an object depends no the mass of the object as well as its speed. The formula for kinetic energy is 1/2 times mass times velocity squared. This means that if the velocity is tripled, the kinetic energy will increase nine times because the velocity is squared. The relationship between work and kinetic energy is that the change is kinetic over time equals the work done. The relationship between kinetic energy and potential energy is that the higher an object goes, the more potential energy it has. The lower it goes/falls the more potential energy it looses and kinetic energy it gains. The formula for finding an objects potential energy is mass times gravity times height.
    The fourth thing I learned about was the Law of Conservation of Energy which states that energy cannot be created or destroyed, it may be transformed from one form into another, but the total amount of energy never changes. This means that in a car the energy used to move the car forward does not disappear it is mearly converted into heat.
    The fifth thing I learned about was machines. Machines help lower the force needed to move an object. The big thing about machines is that there is a work in and a work out. The work out is what force and distance you would have to do without a ramp or a pulley and the work in is the smaller force and bigger distance you would have to do with a ramp or a pulley.
     What I have found difficult about what we have studied this unit is keeping all the different formulas straight and remembering that the change in kinetic energy equals work and not just the kinetic energy. I over came these difficulties by doing problems in class and memorizing which formulas were associated with which concepts so I knew which ones I needed to use. My problem solving skills and effort this unit have not been as strong as they usually are. Though I have completed all my homework and really tried to understand our activities, I have not been persistent in learning the materials and my self-confidence lowered as a result because I did not do very well on quizzes.
     My goal for the next unit is to be persistent in learning things that may prove to be difficult and memorizing the formulas right when we learn them so that I do not struggle throughout the unit and instead can attack each new concept with out having to worry about the last.
     The connections that I can make to the real world are with the three flights of stairs every day versus the elevator on the other side of the building. It is good to know that I get a work out instead of a work in. Another connection I can make is to cars, both with the law of conservation of energy and power. Since my dad is a car dealer I know a thing or two about the engine and it is interesting to understand that the reason cars aren't 100% efficient isn't because any energy is wasted but rather because it is converted into heat.

   

Unit five photo

If a person wanted to get a ball that weighed 200 newtons from the bottom of the arch way to the platform in the middle of the stairs, it would be easier for them to bring it up the stairs rather than throw it. This is because the vertical distance that it will travel will not change, therefore the work will not change. If the work doesn't change, that means that the greater distance the smaller the force. Therefore, because the stairs are a greater distance than the arch way, the force needed to get from the bottom of the stairs to the platform would be way less than if you threw it.

Unit four photo

Why is it that my dog places her paws right below her shoulders when she sits instead of right next to each other like you would expect? The reason for this is if she puts her paws together she lowers her range of base of support therefore making it more difficult to keep her center of gravity above it. So, she keeps her paws spaced out so that she will be able to comfortably sit without worrying about balancing and falling.

Unit Four Blog Reflection

     The first thing that I learned about in this unit was tangential and rotational velocity. Tangential velocity can most easily be described when relating it to a merry go round. When children are playing on a merry go round, the one closest to the center of the unit will be the one with the lowest tangential velocity. This is because it does not need to cover as much distance to make one rotation in the same amount of time as the person on the outside of the merry go round. The person on the outside needs to cover more distance to make one rotation, and therefore needs to travel faster. This is easily relatable to rotational velocity as well. Rotational velocity refers to how many rotations an object makes. Though the kid closest to the center of the merry go round and the kid furthest from the center have different tangential velocities, they have the same rotational velocity. This is because though traveling at different speeds they are both making a full rotation in the same amount of time.
      In this unit the second thing that I learned about was rotational inertia and angular momentum. Rotational inertia measures how quickly an object can spin. An object with high rotational inertia, such as a wooden hoop, spins much slower than an object with a low rotational inertia, such as a steel ball. The reason that a steel ball with low rotational inertia spins more quickly is because their is more mass in the center of the object than a wooden hoop, who has no mass near the center. The more mass that is near the center of an object, the lower rotational inertia. Angular momentum relates to rotational inertia in that it is when an object changes to pull mass either closer or farther towards its center. A great example of this is in ice skating. When ice skaters want to spin in the air or on the ice, they pull their arms into their chest to that they are right next to their axis of rotation, this helps them to complete three full turns in a triple axis. When they land and want to slow down, they put their arms out so they can glide at a regular speed.
    The third thing I learned about was conservation of momentum. This law says that a rotating objects momentum is found with the rotation inertia times the rotational velocity of that object. It also tells us, like we learned in the last unit, that the momentum before is equal to the momentum after.
     The next thing I learned about in this unit was torque, center of gravity, and center of mass. Torque measures the ability for an object to move. The equation for torque is torque equals lever arm times force. The longer the lever arm, the bigger torque. A perfect example of this is a door stop. The closer to the axis of rotation the door stop is, the less force and smaller lever arm and there fore the less easily it holds the door open. When you put the door stop at the end of the door, however, farthest away from its axis of rotation, the lever arm is as long as possible and therefore there is a great force. The center of mass of an object is where it is balanced. For example, if you hold a broom near the bottom of the handle, you can balance it. This because that is where the masses on either side are equal. The center of gravity can most easily be explained through wrestlers. This is the point in an object that holds it up. This means that the center of gravity is normally near the center of an object and it is over the base of support which is the reason why people do not fall over. For example, the center of gravity for humans is normally around their hips. This is why a wrestler bends his knees and lowers his hips so much. The more your center of gravity can be supported by your base of support the more difficult it will be to knock you over. This is also why people that walk on tightropes carry a long stick. The stick lowers their center of gravity therefore making it more difficult for them to fall off the rope.
     The last thing we learned about in Unit four is centripetal and centrifugal motion. Centripetal motion is the force that keeps you in a circle when your turning on a bike, in an airplane, and even on a race track. By drawing vectors, you see that centripetal motion is the force that keeps a stead circle. Centrifugal motion is a fictional force. It is the force that pushes the water out of a washing machine as it empties or pushes you up against the passenger door when you turn a sharp corner. This is not real, it is simply inertia working and the door keeping you inside of the car. An example of this can be found in this picture of the airplane, with the vectors drawn in.

     What I have found difficult in this unit is remember the differences between tangential and rotational velocity and center of mass versus center of gravity. I overcame these difficulties by pairing each concept with a concrete example in my mind so that I always had an easy way to remember it. My problem solving skills and effort this unit have been pretty good. I have tried to complete all my homework to the best of my ability and really pay attention when taking notes and learning new material. I am pretty confident in this unit because I have thought deeply when solving problems and have really gone in depth about each concept that we have learned.
     My goals for next unit are to try to grasp the concepts just by learning them and not by examples so that I am able to apply them easily to everything and I am going to do this by focusing on the concept rather than how I am learning about it.
     The biggest and most clear connection I can make to what we are studying is ice skating. This is because I used to figure skate therefore I have found it fascinating that rotational inertia, angular momentum, center of mass, and center of gravity can all relate to things I have done on ice before. Another connection I can make that I haven't talked about in this post yet is train wheels. Train wheels are designed so that the circle on the outside is smaller than the circle on the inside, as you can see in this picture.

     This is because the smaller side has a higher tangential velocity than the bigger side, and therefore can more quickly correct when turning corners. 

Meter Stick Challenge

My initial plan to solve this challenge was very vague. I was not sure how to tackle the problem at all but I did know that it had something to do with torque. Since I knew the equation for torque was lever arm multiplied by force that is the first thing that I wrote down. Since I knew that there was two torques in this situation I wrote lever arm times force = lever arm times force. I knew that the weight was one hundred grams and since that is mass instead of force I calculated that the force of the weight was .98 newtons. From there I was stuck. However, my group members helped me figure out that the center of gravity of the stick was at the 50 centimeter mark because that is the point at which it balanced like a sea saw on the edge of the table. With the weight on the end, the center of mass was at the 25 centimeter mark. Therefore, we figured that the lever arm lengths were 25 and 75 centimeters. However, we realized that the center of gravity is where the counter clockwise lever arm began. From there, we filled in the equation and the only variable we had left was the force for the clock wise torque. We solved for that and converted it from newtons to grams and got that the meter stick was 100 grams. When we weighed it we found that it was 101 grams. The reason that the meter stick could balance on the center of mass and the center of gravity because in both cases there was an equal force on each side.

Torque

Torque is the ability for something to turn on a certain axis. Torque is equal to lever arm times force. There is a center of gravity of every object and also an axis of rotation. The two are not the same but the torque of each object depends on both. The reason that this diver can flip so many times is because their center of gravity is in their waste and by pulling in both their arms and legs they make their axis of rotation where their center of gravity is as well. Their arms are legs are the level arms and because they are small the force is big therefore making the torque big.

Rotational Inertia and Angular Momentum

In this video you can see that the women is thrown up into the air at a small speed but gains tons of momentum when she is in the air by pulling her arms close together. This is has to do with angular momentum and rotational inertia. High rotational inertia means that most of the weight of an object is away from it's axis therefore making it hard for the object to turn. Low rotational inertia means most of the weight in near the center of the object making it easier to turn. This is when when she brings her arms in it adds weight to her axis therefore helping her turn more quickly, or lowering her rotational inertia. Angular momentum is when there are not many sharp angles on an object making it easier for it to turn or move quickly. This is also why when she draws her arms in she attempts to lay them as flat as possible on her chest, in order to have a lot of momentum by having not a lot of angles.