Unit Three Blog Reflection

In this unit we learned all about Newton's third law. Newton's third law states that every action has an equal and opposite reaction. For example, person pushes wall, wall pushes person. You are probably wondering how anyone ever moves anywhere if this is true. Well, take a horse and buggy for example. Horse pulls buggy, buggy pulls house. Buggy pushes ground down, ground pushes buggy up. This is the important part; horse pushes ground backwards, ground pushes horse forwards. That is why people walk and cars move and also why if you put a magnet in front of a magnetic car, it will not move because they will pull on each other and there is not another force causing them to move. Something that surprised me when learning this is we discovered that when an 18 wheeler and a small prius crash into each other, they both exert the same force because of Newtons third law. The only reason that a small car is more damaged is because it has a smaller force therefore a bigger acceleration, which connects to Newtons second law of acceleration equals net force divided by mass. Another thing we learned about is vectors, which relates to Newton's third law. When someone sleds down a mountain, where does their direction come from? Well, first of all, because of Newton's third law, sled pushes ground down, ground pushes sled up. This force up is equal to the weight of the sled/person, and is called the support force. Gravity, however causes a force to pull the sled directly downward, instead of diagonally downward to the mountain. If you take the support force line and the gravity line and make a square, you can connect the corners to find the actual velocity. This can be applied to which way a boat is going to go across a river with a current, pushing a couch with two people, and an object hanging in mid air connected with one string.

The next thing we learned about was the universal gravitational formula, which is a formula that can tell us lots of things but mostly it informs us about tides. The formula is force equals gravity (which equals around 7 times ten to the negative 11) times mass one multiplied by mass two all divided by the distance between the two squared. Though this sounds complicated, it is easy once you do it. The easiest way to think about this is when you relate it to tides. For example, 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 that side of the earth is very small, since force and distance are inversely proportional in this equation. Obviously, this means that the tides on the right side of the earth are going to be low, because they have less force. This also means that the left side of the earth is a small distance away from the sun, meaning it will have a great force on it. This is why one side of the earth experiences high tides while the other experiences low tides. Now the moon is not always in the same place, so there are two different types of tides. When the moon is either above or below earth, the tides are called neap tides. These tides are higher or lower than normal tides because of the distance it is from the moon. The tides when the moon is on the right or left side of the earth are called spring tides. This is when there is a full or new moon, and the tides are average. Because the moon has a cycle of twenty seven days, the tides are different each day every month, therefore you can not predict them. 

The next thing we learned about after the universal gravitational formula and tides, was momentum and impulse. The formula for momentum is mass multiplied by velocity. We also learned about something called the conservation of momentum, which relates to another formula we learned about called the change in momentum. The formula for change in momentum is p(the symbol for momentum)final minus p initial. This is basically the same thing as the formula for conservation of momentum, however the conservation of momentum breaks down the change in momentum a little more. The conservation of momentum formula is mass one times velocity one plus mass two times velocity two equals mass one plus mass two times velocity one/two (which is the final velocity). Or, MaVa + MbVb = (Ma + Mb) Vab. This can be used to find any one of the variables in the equation, but it is mostly used to find the velocity after the collision. We learned about this through a lab where we took two carts and had them almost touching and then tapped a button which made them be pushes apart and comparing the momentum before to the momentum after. In the same lab we used those carts and had one moving one crash into a non moving one and found the differences in momentum. We learned that the conservation of momentum is directly related to newtons third law. We learned this through formulas. This is what we found:

Fa = -Fb (newtons third law, equal amount of force)

Fa∆t = -Fb∆t (acting for the same time)

Ja = -Jb  (impulse, which I'll explain in a second)

∆Pa= -∆Pb (conservation of momentum)

This is how one equals the other.

The last thing we learned about was impulse. The formula for impulse was j(the symbol for impulse) equals force times change in time. As you saw earlier, this can be related to momentum. The relationship between momentum and impulse is the reason why things like airbags and the mats on gym floors keep us safe. I will explain this through the mats on the gym floors example. The floors for gymnast are covered in pads because the gymnasts are going from moving to not moving. Which means they are going from having momentum to not having any momentum (referring to p=mv and ∆p=pfinal - pinitial). Because of this, the change in momentum wil always be the same no matter how long it takes them to stop. Change in momentum is equal to impulse (J = ∆p), therefore the impulse will also be the same. Because the impulse is force times change in time, the pads allow longer time to stop. The more time it takes to stop, the less force and therefore the less injury. In other words; 

J=f∆t

Or, if the mats were no there and it barely took any time to stop;

J=f∆t

What I have diffcult about all that we have studied is that it is hard to keep all the facts straight in my head. There are lots of formulas along with lots of confusing information that have to do with the same things, and they all originate from Newton’s third law. I have found it challenging to keep them all straight.

I overcame these difficulties, however, by relating each one to the different examples we learned in class. Once you relate it to an example in real life that we learned about in class, it is much easier to keep it all straight.

My effort in this unit has been up and down. Though I want to get a good grade, I often got frustrated with the difficult concepts that we were learning and at times I sort of gave up. However, the more close attention I paid to my homework and the harder I studied for quizzes the more that I found that I could do it and know exactly what was going on with a little big of hard work. My homework was pretty hard effort but my blog postings and class effort could have been stronger, which I have been trying to improve towards the end of the unit. I could have been a lot more persistent and creative, and my self-confidence was definitely not high. However, I thought my problem solving skills in this unit were particularly good, considering the past view have been very bad. I think my group members and I communicated very well however I could have had more patience in understand the problems.

My goal for the next unit is to always be persistent in believing that I will understand a topic no matter how difficult. I plan to do this by going in for extra help if I need it and always completing my homework with my full effort.

Besides the connections we made in class to everyday life, there are tons of things that this unit can be related to. An egg toss with conservation of momentum and impulse, car crashes, catching and throwing balls, and many other things. The main thing I think about when I think about this unit is throwing my phone from across the room. When I want to leave my dorm room and I need to put my phone down, I almost always throw it on my bed. I try to lean over to get as close as I can, and I pull my arm down so that the curve of my phone is higher. Now, I know why because of change in momentum, the universal distance formula, and impulse. 

Momentum and Impulse Picture

This is a picture of my friend Emily playing soccer. If Emily pulls this ball back with a force of 10m/s and the ball weighs 20kg, then the ball will have two hundred meters kilograms per second momentum because the formula for finding the momentum of an object is mass times velocity.

Impulse and Momentum of a Baseball

This video is a very quick summation of impulse and momentum. It talks about the equation for impulse, which is the force times the time, and it also tells us that impulse is equal to the change in momentum. The one thing that this video talked about that was different from what we learned in class is that the change is moment is equal to the mass times the change in velocity. In class we learned that the change in moment is equal to the final momentum times the initial momentum. Though these two things equal the same thing, it might be easier to stick to the one we learned in class. Other than that, this video is a really good short explanation and summary of impulse and momentum and how they relate to each other.

Tides Recourse

Unit Two Reflection

In unit two of physics, the first thing we learned about was newton's second law of motion. This law states that acceleration is directly proportional to force and inversely proportional to mass. This means that if the force increases, the acceleration will also increase. It also means that if mass decreases, the acceleration will increase. The lab that we did on this concept involved a cart, weights, and a hanging weight. We moved the weights around from the hanging weight to the cart and measured the acceleration on each change. In the lab, we constantly kept one thing concept. For example, we kept the force (or the weight on the hanging weight) constant and changed the mass of the whole system. Or, we kept the mass the same and changed the weight of the force (or the hanging weight). Through this, we found that acceleration is in fact directly proportional to force, meaning when one increases so does the other, and that mass is inversely proportional to acceleration. Meaning when one decreases, so does the other.

The next thing we learned about in physics was objects in free fall. In free fall, objects do not have air resistance and therefore only have the force of gravity act on it. The force of gravity is known to be 9.8 m/s squared. The two equations used when talking about free fall is velocity equals gravity times time and distance equals 1/2 gravity times time squared. We learned that acceleration is free fall is constant, meaning each second and object is gaining a speed of 9.8m/s^2. We also learned that in free fall, a penny and a feather will hit the ground at the same time because the only force acting on them is gravity. The lab that we did to demonstrate free fall was we used a steal ball to measure the height of third anderson. We did this by dropping the ball from the third floor, the top one, and recording the time it took for the ball to fall from the top of the floor to hit the ground. Using the average of a few different trails, we plugged this into the d=1/2gt^2 formula and found that our estimated height of third anderson was about 9 meters. Then, we took string and found that the actual distance was a little bit under 11, pretty close. 

The next thing we learned about was something similar to free fall but much more complicated. It's called projectile motion. Projectile motion is the affects on an object that does have air resistance and factors in the horizontal motion of an object. To get the horizontal velocity of an object you use the formula v=d/t. Of course, this can be rearranged to find the horizontal distance or how long an object traveled horizontally. Something that is different between vertical and horizontal velocity is that horizontal velocity stays constant throughout the time something is traveling through the air. However, vertical velocity gains 9.8m/s^2 each second when falling downward and looses 9.8m/s^2 when going upward. Projectile motion is used a lot when talking about skydiving. This is because when you are skydiving you are not free falling because you are greatly affected by air resistance. Once a person jumps out of a plane, they gain velocity as they fall until they reach something called terminal velocity. In terminal velocity, the weight of the object is equal to the air resistance on the object, causing the velocity to stay constant until something changes. This means that as the velocity increases, before terminal velocity, the acceleration is decreasing and is at 0 when the object is in terminal velocity. Once a parachutist reaches terminal velocity they can only stay there for a few seconds because they need to deploy their parachute on time in order to not get hurt when they hit the ground. The parachute helps the parachutist slow down, as we learned, because the two things that affect air resistance are surface area and speed. This means that the parachute adds surface area which also adds air resistance, causing the parachutist to slow down until the air resistance yet again equals its weight. However, this new terminal velocity is a lot slower than the original one due to the surface area of the parachute. Also, during this change the acceleration is not just decreasing but it is decelerating into the negatives. Projectile motion is not only used with parachutist, it can also be used with throwing things upward like shooting a cannon, throwing things downward like kicking a ball over a cliff, and dropping things out of air planes. The biggest example besides parachuting that we learned about was the difference between a falling piece of regular paper and crumpled up paper. Though it may seem like crumpling up paper could change its weight, causing it to fall faster, both of these things are incorrect. The reason that a crumpled up piece of paper falls faster than a regular piece of paper is simply due to surface area. Because the normal piece of paper has a bigger surface area, it is going to need more air resistance and therefore is going to take longer to reach a terminal velocity than a crumpled up piece of paper. 

What I have found difficult in what I have studied is separating each formula with each concept and not confusing the affects of gravity on an object in free fall compared to projectile motion. I overcame these difficulties, however, by really paying attention to each example and what they taught about the topic and how I could differentiate each concept by pairing them with their examples in my mind. 

My effort this unit, in my opinion, was even more than last unit. With the many different very difficult concepts we were learning I had to study even harder and make sure that I understood everything outside of class. Though this doesn't reflect in my grade, I felt pretty confident with the concepts because I understood a lot of the things we did in class. I thought that I problem solved pretty well in the labs and that I could express the concepts in both my spoken and written words. I tried to be patient with the work although at times it was difficult when the concepts became difficult, but altogether I thought that it was a strong unit regarding my work effort. 

My goal for the next unit, again, is to study more by completing every assignment on time even if I'm not 100% sure its right because I know now that learning from your mistakes is one of the best ways to learn.

Connections from this lab to everyday life are obvious; parachuting, things falling out of air planes, falling pieces of paper, exedra. But one thing that I noticed in everyday life that applied to physics that caught my eye was a balloon floating up to the sky. Though I'd seen it many times before, I had never though of the physics behind it. 

Falling Through the Air Recourse

In this video, the guy is asking random people if they think the heavier ball and the lighter ball will hit the ground at the same time or not. Most people, incorrectly, say that they will hit the ground at the same time because the force of gravity on both of them is the same. This is wrong because the heavier ball will fall faster in order to reach terminal velocity, a state in which the resistance and the weight of the ball are equal. This is because when air resistance is being factored in to something falling from the air, we know that acceleration is equal to the net force of the object minus the air resistance on the object divided by the weight of the object. Therefore, the heavier the object the faster it must fall in order to reach terminal velocity, while the lighter object reaches terminal velocity more quick, and is passed by the other object.

Physics when Punting a Soccer Ball

This is a picture of Michael kicking a ball straight up into the air. If we know that Michael kicks this ball with a velocity of 40 meters per second, we can figure out not only how long the ball is in the air, but how high it was at its highest point. Because the force of gravity is 10m/s, we know that the ball's velocity looses 10m/s each second. Therefore, to reach the top of it's path the ball must travel up in the air for 4 seconds. Then, since objects gain 10m/s each second when falling down, the ball will take 4 more seconds to return to Michaels foot. This concludes a total of 8 seconds. Then, using the distance formula (d=1/2gt(squared)) we can plug in 4 seconds, the point when it is the highest, to find out how high it went.
d=1/2gt(squared)
d=1/2(10)(8) squared
d=40 meters.

Free Fall: the Affects of Gravity

In this video Bill Nye is throwing different objects of different weights off of a parking deck and onto a target three stories below. The time each object took to hit the ground after leaving Nye's hands is the same, even though we didn't time it. You can tell this from watching the video, but also because we know that the force of gravity on objects is always 10 m/s squared, when you disregard air resistance. Because of this each object took the same amount of time to hit the ground.

Newton's Second Law Resource

In this video he is talking about the second law of motion and unlike the equation we use in class he uses the equation force equals mass multiplied by acceleration. He's using a red ball and a yellow ball and the red ball is heavier then the yellow ball. Therefore, they have a different mass. The force is the same and will be the same for both of the balls in the cannons with acceleration. You can physically see that the heavier ball was going far slower and lower than the yellow ball which was lighter. This proves that acceleration is inversely proportional to mass meaning the more mass the less acceleration and the less mass the more acceleration.

Unit 1-Motion

In this unit of physics I learned about motion. The first thing I learned about was Newtons first law of motion, the law of inertia. This law states that an object in motion will stay in motion unless acted upon by an outside force. It also stays that an object at rest will stay at rest unless acted upon by an outside force. We learned a lot about inertia through riding the hovercraft. We learned that inertia is directly related to mass and that the more mass something has the more inertia it has. Another thing we learned more about through the hovercraft lab was velocity. Velocity is the speed and direction of an object at any given time. The units for velocity is m/s. An object can only have a constant velocity if it has an unchanging speed and is going in only one direction. This means that if an object is rounding a corner, even if it maintains the same speed throughout the whole curve, it does not have constant velocity. The formulas we used for velocity were, for how fast, velocity(v) equals distance(d) over time(t). Or, v=d/t. The formula we used for how far was distance(d) equals velocity(v) times time(t). Or, d=vt. Another thing we learned about constant velocity is that when an object has constant velocity it means the net force is zero meaning it is in equilibrium. Net force is the force that is on an object. For example, if a person pushes a box with 200 newtons of force and the friction on the box is only 150 newtons, the net force of the box would be 50 newtons in the direction that the person is pushing. The last thing about motion that we learned about is called acceleration. Acceleration, though this sounds confusing, is how fast something is getting faster. For example, if a car is speeding up with a constant acceleration of 5 m/s^2 and it starts with a speed of 10m/s, then it will go an extra 5 meters for every second. The formula we learned for this was velocity(v) equals acceleration(a) times time(t). Or, v=at. This is the formula we used for acceleration when trying to determine how fast something was going at any of the given variables. The formula that we used for how far something had gone at any given variable was distance(d) equals one half acceleration(a) times time squared. Or, d=1/2at^2. 

What I have found difficult about what I have studied is really grasping the concept of inertia and understanding that something can be moving and will never ever stop unless some sort of force gets in its way or makes it stop. I also had a lot of trouble understanding the concept of acceleration and that it is a rate of how fast something is getting faster. The last concept I had trouble with was that of the different velocity and acceleration rates on an inclined plane.

The way I overcame these difficulties was actually through the labs we did in class. The lab with the marble helped me a lot with acceleration and incline confusion because I could physically see how the marks between each second got farther apart on an inclined plane as compared to them being exactly the same length apart on a flat plane. The way I understood inertia, the moment it clicked for me, was during the lab in the hovercraft when I saw that it would truly stay in the same place or travel until it hit the wall unless someone was there to stop it. 

My problem solving skills and effort towards class have been pretty good in my opinion. I don't really talk a lot in class but I think I ask questions when I don't understand something and I put it a lot of effort towards completing each assignment and understanding it once I complete it. I try really hard to do all the homework which I think helps a lot because it always helps me understand the concept that we are learning at that time. This is because it gives me a chance to really work it out for myself and I think that I have been putting a lot of effort towards homework so far. I am not really a "blogger" per say but I do try to include everything in each blog post and explain to my "readers" that I really know the material and that I could teach it to them. I think my use of creativity is lacking a little bit just because the only thing that I use to help me understand concepts is the labs. Though those help me to completely get a topic I think I could probably think outside the box and come up with my own ideas instead of using the ones from the textbook. I do, however, think my self-confidence in physics is pretty high because I know that even if I don't understand something right then I will eventually get it through all the different things we do to really dissect each topic.  I think communicating both by my spoken and written words could probably improve when it comes to spoke. As I said earlier I do not like to speak in class much at all but I think with the voice thread that is a really good way to get my voice heard because it is simply explaining that I know a topic and in class I normally don't have questions anyway.

My goals for the next unit is to be more creative when thinking about different ways concepts could apply to everyday life and to speak in class more. Also to not make the mistake I did on the trip problem again and really read over everything carefully until I fully understand what I am being asked.

The connections that I can make through situations in the world is, similar to the football question that we had on the test, a connection to soccer. The bigger people are put on defense while the smaller, slimmer, and faster people are put up top at forward. This is because the law of inertia shows us that the more mass a person has the more inertia. Therefore, a smaller person has a much easier time beginning to run toward the goal then a bigger person. Likewise, a bigger person is much harder to stop moving but also harder to start moving. This is why each person is put in a particular position. Another connection I can make to real life is to acceleration. Almost all kids love to get down on their backs and roll down a really steep hill. As kids, we view it as fun, but now that I've taken physics I am able to see why what happens happens. When you start rolling you move rather slowly, but you gradually get faster and faster until it feels like you are barely touching the hill at all. I now know that this is because you are accelerating and a constant rate. I also know that the only reason you slow down at the end of the hill is due to the friction between the ground and you.

This is a video I made with two other people in my class that, hopefully, should help clarify the concept of velocity. 

Intertia Picture

In this picture, my parents are putting up my christmas tree from this past christmas. As you can see, it accidentally tipped over, and my dad had to catch it as it was falling. If the only thing holding it up normally is the little red thing that our family puts it in, why doesn't it fall over more often? Well, according to Newtons first law of motion, the law of inertia, an object at rest will stay at rest unless an outside force acts upon it. Similarly, it states that an object in motion will stay in motion unless a force is acted upon it. This is why the christmas tree stays standing when all thats holding it up is that little red stand, and also why when my mom tipped it over it would have hit the ground if my dad had not been there to catch it.

Constant Velocity Vs. Constant Acceleration

The purpose of the lab that our class recently did with the marble is to physically be able to observe the difference in constant velocity and constant acceleration. Constant velocity means that something is rolling with not only constant speed but also in a constant direction. This means that, like the marble, the object is going the same amount of distance for each unit of time. For example, a car is driving in a straight line at 60 miles per hour (meaning it has constant velocity) constant velocity tells us that for every hour the car will go 60 miles, as long as it maintains its speed and direction. Constant acceleration, on the other hand, is when the car is getting faster at a constant rate. This is a little harder to understand than constant velocity, but it's a similar concept. If something, like the marble we used in the lab, is traveling with constant acceleration, it means that it will travel a farther distance than it did before for each unit of time. For example, if a car is speeding up with a constant acceleration of 5 miles per hour and it was originally going 40 miles per hour, it means that in the first hour it will travel 40 miles, the next it will travel 45, the next 50, and so on.
The way that me and my partner conducted this lab was, first, we drew a starting line for the marble. After the timer was turned on and we went through a few practice rounds, we rolled the ball at a constant speed and marked its place each time the timer sounded with chalk (so each second). After we managed to do this in a straight line, we measured the distance between each chalk mark and recorded what we found. We did this once on a flat table and once with the table raised on one side. Looking at each line, it was clear to see that the flat table displayed constant velocity and the table with the raised side displayed constant acceleration. This is because the flat table had an equal distance in between each chalk marking where as the raised table had more distance than the last between each chalk mark. After getting all of our information we put it into a chart on excel and graphed it. From there you could also clearly see the difference between velocity and acceleration because the graph of velocity was a straight line and the graph of the acceleration was a curve.
What I found out about how constant acceleration and constant velocity compare is that you can not have both at the same time. Because constant velocity implies constant speed, and constant acceleration implies speeding up at a certain rate, you can not have them both, ever. I also discovered that even though you can not have both, they are someone similar in that they are both a pattern. They are different in that constant velocity is one speed and therefore had a graph with a straight line and constant acceleration is changing speed therefore the graph is a curve.
The formulas used for constant acceleration are as follows; if you want to find how fast something with constant velocity goes you can use v (velocity) equals d (distance) divided by t (time). If you want to find out how far something with constant velocity goes you can simply rearrange that equation and get d (distance) equals v(velocity) times t(time). When it comes to acceleration, if you want to find out how fast something is going you use v(velocity, or speed) equals a (acceleration rate) times t (time). If you want to find out how far something with constant acceleration goes you can use the equation d (distance) equals one half a (acceleration) times t (time) squared. In that order, this is what the equations should look like:
-v=d/t
-d=vt
-v=at
-d=1/2at^2
The graphs that we found at the end of our lab by putting in all of our information showed a lot about constant velocity and acceleration. The graph of constant velocity was a straight upward line where as the graph of constant acceleration was an upward curve. The constant velocity graph was a straight line because nothing was changing. The only thing that was happening to the marble in this graph was that as more time went on more distance was gained. The constant acceleration graph, on the other hand, was a curve upward. This is because the speed was varying and as more time went on more distance was gained between each second.
The way we used the graph to help support the information that we found was we plugged the information in and got an equation out. This equation could be lined up with the equation v=d/t (the equation used to find how fast something goes with constant velocity). When we plugged both a distance and time in, both equations gave us almost identical answers. This meant that we had gotten near perfect data and that the marble was in fact rolling with constant acceleration or, in the other case, constant velocity.
A few important things that I learned from this lab that will help me for the future are, first of all, the different formulas. These will help a lot with finding the velocity and acceleration of objects in the future. Another thing I learned was that finding accurate data is a must because otherwise you can not actually understand what you are doing. The last important thing that I learned through this lab is that physics really can be applied to everyday life, even if you don't see it at first.

Trip Question

My initial thought on the answer to the trip problem was 60 mph, which as we discussed is what most people think the answer is at first. I thought that was the answer because the only thing I payed attention to in the problem was the average miles per hour instead of looking more into the per hour part. Because I only looked at the average, I added up the three speeds that would get the driver an average of 60 and figured "that was easy!" This was, obviously, not the correct answer. I learned that I need to read the problem carefully and figure out exactly what I am trying to find instead of basing everything off of my first impression.
The correct answer to the problem, which we found out later, is that the car needs to travel faster than the speed of light to go an average of 40 km/h in one hour. In order to solve this problem, you need to know the following. You need to know that the driver wants to travel 40 km/h in one hour. He has already driven 20 kilometers at an average of 40 km/h and then 10 kilometers for an average of 20 km/h. You also need to know that speed equals distance divided by time. If you rearrange that, you can get that time equals distance divided by speed. Therefore, for the 20 kilometers going 40 km/h equals .5, which is hours translates to half an hour. The 10 kilometers going 20km/h also translates to .5, which means the driver has already traveled an hour. Therefore, because he has already traveled an hour, he must immediately get to the end of the 40 kilometers, and the only way to do that is to travel at the speed of light.
What I learned about my problem solving skills is that I've been trained to skim over the problem and quickly solve it for what I think is the write answer. I will remember, after this experience, that I need to read the problem carefully and write things down in order to know how to get the correct answer.

Acceleration

http://www.youtube.com/watch?v=Vofs4znLgBQ

This is a video of a BMW speeding up as fast as it can showing its high acceleration rate. The car goes from stopped to a very high speed in just a few seconds. When the car is going straight it has a constant velocity. When the car is turning, however, it only has a constant acceleration because you can not have constant velocity without the object going in only one direction.

The Hovercraft Experience

In class on wednesday, we got the opportunity to ride on a hovercraft. Riding on a hovercraft feels much different than riding on a plane or a boat. The hovercraft is uncontrollable, no forces are acting on it but the person pushing you across the gym. Basically, you are literally just floating without any control of your direction. Riding on, for example, a sled, is much different than riding on a hovercraft because in a sled you have control of how fast you are going or the general direction that you want to glide down the hill. In a hovercraft, you really are able to understand the feeling of being an object in motion staying in motion. A sled stops at the bottom of the hill because you were the force that caused it to go down in the first place. A hovercraft never stops unless another person or force causes it to.
I learned that the more mass one person has the harder it will be to be the force that stops them. I also learned that because of the pull of gravity and a thing called support force, an object has the ability to be moving with a net force of zero. The last thing I learned was that an object can be in equilibrium when the forces are positive and negative and equal causing it to have a net force of zero.
Acceleration, based on this lab, seems to depend on the amount of force an object is given and also its mass. The bigger the person on the hovercraft, the harder one had to push to make them go the same speed as a smaller person.
I would expect to have constant velocity when I pushed off on ice skates and glided there down the ice. Or, as we discussed in class, when I am skydiving and I reach a certain speed and then the support force matches the pull of gravity; causing me to fall at a constant rate.
Some members where harder to stop than others because some members had more mass than others. The more mass, the more force was needed to stop them.

Triple Axel: Inertia

http://www.youtube.com/watch?NR=1&feature=fvwp&v=yN9NyevGir8


In this video, a girl is doing a figure skating trick called a triple axel. In the first few seconds of the video, she is gliding on ice at a constant speed because she caused herself to go that speed and the law of inertia states that an object in motion stays in motion and due to the lack of friction between the ice and the skates she stays in constant motion.

How is Ice Skating science?

     In physics this year, I expect to learn why things are the way they are. For example, as we discussed in class today, why we have seat belts, why air bags keep us safe, how credit cards work, the secrets to winning a game of tug of war, why an ice skater's speed increases when they pull their arms closer to their chest, and many other things of this nature.
     A question that is often asked by students is why we are learning the material we are given. Well, I think that studying physics is important because, personally, I like to know the reason behind things. We all know about the law of gravity, but I don't think that I know anyone that knows why gravity is a law. Aside from learning the reasoning behind things, learning physics is important because we see and use physics everyday of our lives. For example; the lights turning green at stop lights when you are waiting to turn left, or sticking our feet in the sand until the tide touches our toes, and even the gift of sight. Another reason that learning physics is important is because knowing that all of these everyday things are caused by physics can allow us to create even more things that are useful in our everyday life. Seat belts, stop lights, baseball, tug of war, and ice skating were all, most likely, figured out and some even created by physicist. With more knowledge we can create and give a reason behind the unknown.
       When I signed up for the class physics, I realized I didn't know much about the course material. The questions I have about the class physics are as follows; How can you define physics? How were the things we are going to learn in physics discovered? Can more of ice skating, not just pulling your arms to your body in a spin, be applied to physics? And, what kind of things are we going to do to help us to learn how physics applies to everyday life?
     The goals I have for myself in physics this year are as follows:
          1.) To earn at least a 90 percent in the overall class average.
          2.) To learn more about how physics applies to everyday life.
          3.) To understand all the concepts that are introduced.
          4.) To improve how to write about science.