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.