Unit Reflection!

Chapter Reflection

What I learned….

This chapter we learned about many important concepts such as work, power, Kinetic Energy, Potential Energy, and the law of conservation of energy. First, we started off by learning about Work.

Work=force x distance

I learned that work is the effort exerted on something that will change its energy, and that no work is done on an object if it is carried parallel to the earth on a flat surface. A good example of a work problem is: If Tom carries a 10kg weight up a 10ft. high set of stairs, how much work is done?

Work=10(force)x10(distance)

=

100 Joules (work is measured in joules)

Next, we went on to learning about power!

Power=work/time (so essentially how long it takes you to get work done)

Now lets say it took Tom 5 seconds to get up the stairs. I would be able to solve by using the power equation

Power=100/5= 20 watts

After learning about power and work we began to learn about Kinetic Energy. During this I learned that the change in Kinetic energy is equal to the amount of work done.

KE=1/2mv²

Example Problem: How much work was done if a 10kg car was going 20 mph?

KE=1/2(10)20²

=2,000 joules

After learning about Kinetic energy I went on to learn about Mechanical Energy. During this section I learned that mechanical energy is the energy due to the position of something or the movement of something, and includes potential energy. I then learned that potential energy is stored energy held in readiness.

PE=mass x gravity x height

Then came the conservation of energy! The conservation of energy states that energy cannot be created or destroyed. It may be transformed from one form to another but the total amount of energy never changes. I a learned that energy in=energy out and work in=work out in this section. We then went on to learning about the work energy theorem which by using the equation for KE states that if for example a car is moving 2x the speed of another, it will take 4x as much work to stop, and if it is moving 4x the speed of another it will take 16x as much work to stop. After learning about the law of conservation of energy, we were shown an example of a pendulum swinging to demonstrate that an object cannot gain or lose energy. Each time the pendulum was swinging, it only reached the point that it was let go at, and didn’t go any further up because of energy’s conservation energy in=energy out.

What I found difficult…

This unit, I found that work and power were fairly easy concepts to grasp, but once we began to learn about kinetic and potential energy, I found the questions more demanding. Kinetic Energy, which equals ½ mv²  seemed easy enough to understand but once we began using the equations I felt more confused. Through practice though I was able to understand the concepts. Another concept I found difficult was the pulley system. It didn’t make sense to me at first how the system worked and how the force was cut in half when using 2 pulleys, but after going over the questions asked from the lab that we did involving Ms. Lawrence’s car, I felt as if the concept had been cleared up. This section I felt challenged by the class and mousetrap car, But through hard work I was able to understand the concepts.

Connections to the real world…

I feel as if every section in physics that we learn, I am able to find a stronger connection to in my everyday life. Perhaps this is because we build upon the lessons that we have already learned. This section I was able to connect the law of conservation of energy to, well, basically any object that uses energy. As we learned about the law of conservation of energy which states that energy cannot be destroyed or created, but only transformed. With this I was able to connect KE and PE to every day objects such as roller coasters! I learned that roller coasters are designed by using the law conservation of energy and by knowing that energy must equal energy out and the change in kinetic energy is equal to the change in potential energy, the coaster will not lose or gain energy, therefore the first hill is the largest so it will have the ability to get across the other hills, because the potential energy is the highest at the top of the hill, and lowest when in motion it will continue to maintain its energy and coast. I was also able to find connections to work and power when we first did the lab involving everyone running up the stairs, then walking, and then running with a weight.  I realized that the work is always the same no matter how fast you do it, but the power is the thing which actually changes. We then were able to calculate our horsepowers when running up the stairs which I though was pretty cool!

Problem Solving Skills…

Over this past section I believe my problem solving skills have improved. With the work and power problems finding the answers were fairly easy, but the kinetic and potential energy questions challenged me. Once learning that the change in KE=the change in PE and that work in=work out, solving the force problems got easier but were still arduous questions. Some of the problem solving questions that involve efficiency were also hard at times, but once I studied the material and took time to go over my notes to understand the concept better, I found that It was much easier to solve problems involving conservation of energy.

Final Mousetrap Blog

Final Mousetrap car report
a.     Newton’s first which states that and object in motion will stay in motion and an object at rest will stay at rest unless a net force acts upon it relates to the mousetrap car because It helped Natalia and I understand what the reasons for our law applies to the performance of my car because on our nonsuccess with the car due to friction. We learned that the car wanted to continue to move, but because certain things like the placement of the wheels got in the way, it was not able to go the 5-meter requirement. Newton’s second law, which states that acceleration is equal to net force over the mass of the object also relates to the car. During our journey, we realized that the car was not able to go very far because it did not have a big enough force exerted on it. Because a=fnet/m, we realized that we needed to add a greater net force in order for the mousetrap car to accelerate so we added a weight to the car. Once we added the weight, we noticed a significant improvement in the car’s speed and distance because it was given more acceleration. Newton’s third law also applied to our project. The third law states that every action has an equal and opposite reaction. I was able to connect this to the car’s situation because the energy that propelled the wheels was the energy that was derived from the mousetrap, and so the mousetrap's equal and opposite reaction was to accelerate. Another action and reaction pair that I noticed was when I pulled the actual trap backwards in order to wind the wheels up, the trap would push forwards. Going back to Newton’s first law, the trap wanted to stay at rest, but I was the net force that acted upon the trap, and so it was set into motion!
b.      The two types of friction present in the mousetrap car were the friction on the wheels against the ground and the friction within the axel and lever arm. On our car, friction was increased for stability on the wheels by using duck tape on the edges of the back wheels and rubber wheels on the front. In order to make sure the axel for the wheels would not rub the actual mousetrap we had to set them a significant distance apart, because if they were to touch, the car would apply friction to the axel and slow the rotation of the wheels down immensely. We also had to make sure that the wheels were able to turn easily on the laminate flooring, and so we chose to have rubber on the front wheels to provide traction and support, and duck tape on the edge of the back wheels to increase the overall stability of the car, which helped greatly!
c.      When deciding the number of wheels, we chose to have four because it would balance and stabilize the mousetrap, but we did not think the size of the wheels would be very important, but we were wrong. We started with two larger wheels at the back of the car and two smaller wheels at the front in order for the larger wheels to propel the smaller ones with more force, but still the wheels were only about 1-2 inches long, and relatively small. We began trying different ways to increase the speed in the middle of the mousetrap car process without realizing that the wheels might be the problem until the were end. Towards the end of our project, we decided to try CDs as our back two wheels because the more rotational inertia would mean the greater distance achieved in each rotation; which would ultimately make the car faster, and so the CDs with a cardboard support system were put on the mousetrap car, and did make the car measurably faster!
d.     The conservation of energy, which states that energy cannot be created or destroyed, but transformed from one form to another relates to how our car was powered. By having a long lever arm, we increased the amount of energy and torque within the lever, and as we pushed it further back, the PE was increased. Once we let go the PE transformed to KE and propelled the car forwards. Once we kept our lever arm the same, it was only a matter of properly winding the lever arm up and letting go carefully to power the car to go far distances, since the amount of energy in the car did not change. As the car was moving, it was using the spring’s energy and transforming it to kinetic energy, but while we were winding the car up, it was storing the energy as potential energy, for when the lever arm was let go.
e.     The length of the lever arm on the mousetrap car was an aspect of the car that changed frequently along with small changes with the car. We started with a relatively small lever arm, believing that the length would not matter for the 5m distance that was required, but as we progressed in the project, we realized that in order to go the distance, a much longer lever arm would be needed. Using kabob sticks, we connected the longer lever arm to the trap, but the more it was used, the weaker the wood became because the force of the lever arm was so strong. We made adjustments to the wooden stick and used a metal stick instead, which seemed to make the car go much faster. With the knowledge that torque=lever arm x force I knew that in order to make the car have more torque and eventually go faster, a larger lever arm was needed, and the force of the heavier metal stick propelled the car. The further back the car’s lever arm was pulled, the more force that was created, which made the power output of the mousetrap car greater.
f.      Rotational Inertia and Rotational Velocity and Tangential Velocity all related to the tires’ size and rotation. At the beginning, we used relatively small wheels that we got from the dollar store, but trial after trial, the car wouldn’t go very far, and I realized that if the rotational inertia was increased by having larger tires, and therefore having the wheels cover a larger distance per rotation, along with increasing the rate of rotation. To fix the wheel problem, we decided to use CDs as wheels and support them by putting cardboard around the wheels so that the wheels would be stabilized. Once the rotational inertia was increased with the larger tires, and it was covering a larger distance per rotation the car substantially increased in speed.
g.     We are not able to calculate the amount of work the spring does on the car because work=force x distance and in order to find this out we must know the force that the spring exerts on the car, which is impossible for us to find out without using special devices. Potential energy=mass x gravity x height, but the spring has a force of its own that we are not able to calculate. Because the change in KE=the change in PE, and we are not able to calculate the force, we are also not able to calculate how much KE and PE there is at one time while the spring does work. A=fnet/m, and although we know the mass, we still do not know the net force that the spring exerts on the rest of the car, and therefore we are not able to calculate the acceleration.
Reflection
a.     Over the course of the entire mousetrap project, our plans and car changed drastically. We started out planning on using much smaller wheels for our car, along with a lever arm that is about 3x as small as the lever that we ended up using. As we made adjustments, we learned what helped and did not help the car, such as larger wheels made the car cover a larger distance per rotation, and a larger lever arm increased the torque of the car, giving it the ability to go a longer distance. In order to succeed, we had to make the changes when we saw that our car was lacking speed and stability, and so we made the wheels much more stable with a support system made out of cardboard. I would say that we definitely learned from our mistakes.
b.     Starting out with smaller wheels definitely set us back, but when we decided to change the wheels for a larger set, even bigger problems we raised. We were not able to find stable wheels, and so we made them out of cardboard and paper cups. After trying the wheels out a few times, the car fell apart, and then we really needed to find more stable wheels that would not go lopsided while in motion. After finally finding 2 CDs as back wheels, we felt that we were prepared again to go forward in the competition once they had a secure support system of duck tape and cardboard sides.
c.      Seeing that we have yet to finish the car, in the future I would start out my making sure that my mousetrap had very stable wheels and a larger basis   for the car that uses more than just the trap in order to provide force and increase the work. Knowing what I know now, I would have also immediately increased the lever arm to hope that it would help propel the car more. Although the project was at times frustrating and challenging, it was fun way to incorporate everything that we have learned this year into a project!

Mouse Trap Car Day 2

On day two, Natalia and my's original plan was to finish constructing the car, and go straight to performing in the time trial, but that is of course, not the way things went!

Natalia and I started out by finishing up on drilling the holes in the mousetrap and wheels, with only a few setbacks which included cracking both the wood on the mouse trap and the plastic tires. (whoops!) 

Once tiny holes had been drilled into our mousetrap, we prepared to screw the eye hooks into the pre-made holes. Although the eye hooks did crack some of the VERY delicate plywood used for the mousetrap, we were able to securely fasten the eye hooks to the mousetrap, which meant that we were ready for phase 3:

Assembling the Tires! 

We began the task of constructing the axel for the tires and positioning the tires on the axel with confidence, but as time passed, we realized that the original plan of securing the tires with zip ties was not going to be the most effective way to fasten the tires. The zip ties took up a lot of space and were not very secure so we decided to try plain tape instead. To our surprise, the tape was a much more effective way to both keep the tires on the axel and make sure that the tires would rotate with the axel. 

Although it took many different methods of construction, we are on our way to a great mousetrap car!

Mouse Trap Car Diagram!

Mouse Trap Car: Day1

Today was our first day of construction on the mousetrap car! Natalia and I started by attempting to remove the wheels from the toy car that we bought, thinking that the wheels would provide and realistic aspect to the car (and also add some speed!) With high hopes we began to take apart the car, hoping to easily take the wheels off, but that is the opposite of what happened. We used a screwdriver, our bare hands, a drill, and even a hammer, but it was very hard (almost impossible!) to separate the wheels from the car, and once we finally did get them separated, we discovered that their was no axel connecting the wheels, and instead some screws! That was upsetting, but we decided to come up with a new plan. Using a wooden stick that we bought at Lowes, we decided to make our own axel for the car my using a drill to drill holes in the wheels, providing a hole to put the stick through. This ultimately will connect our mousetrap car. Although we did not get much done because of the unplanned for difficulties, we are one step closer to creating our mousetrap car!

Mouse Trap Car: Supplies

The Mousetrap car project was an unexpected challenge! Both my partner and myself have never made, let alone heard of a mousetrap car, but with some helpful videos on YouTube such as this one.I was able to understand that a mousetrap car is actually built using a mousetrap as the “engine”. In the video the creation of a mousetrap car is shown successfully. By taking some of the videos information and also using our physics knowledge, we will be able to create a mousetrap car in order to win this race we must create a practical but fast car.  Here is a list of supplies needed for the winning car…

1.   .Eye hooks (used to connect the car and wheels by drilling small holes into the mousetrap car)

2.    A mousetrap!

3.   Wheels (we decided to use wheels from a toy truck bought at the dollar store, because the wheels would act as more realistic wheels than wheels we made ourselves)

4.    A thin wooden stick to increase the lever arm of the mousetrap to give a greater force to propel the contraption

5.    Zip ties to act as an adhesive for the mousetrap’s wheels

6.    Fishing line

The car that we bought to disassemble and use the wheels for our own car!

Once we have all of these items, we will be ready to begin assembling the car, and eventually win the race!