Work-Kinetic Energy Theorem Activity

Lab #11
Ana Leyva, Ricardo Gonzalez, Chris Garcia
4/19/17

For the different experiments in this lab we are trying to prove that the change in kinetic energy is equal to the work done by the object. In order to do this we did different experiments graphs that would help us prove this theory.

EXPT 1. Work done by a constant force

To do this experiment we first had to set up a track, a pulley at the end of the table and a motion detector on the opposite side of the track. We then tied a piece of string that was long enough to our cart on top of the pulley and attached 50 g to the other side of the string that was hanging over the table. Finally we ran the motion sensor and gave our cart a push so that it would move at a constant speed. This gave us a force vs position graph and a kinetic energy vs position graph that we used to see if the kinetic energy would be equal to the work done.

10. Integral value = 0.1011 N*m        KE value = 0.098 J
- The value of the integral gives the area under the Force vs. Position graph which is equal to the work done. Therefore the integral equals the work done.
-Ideally, integral should be equal to the kinetic energy therefore integral - kinetic energy = 0
           0.1011-0.098= .0031 which is not equal to zero  however it is a relatively very small number and we can still conclude that the integral = kinetic energy.    

11. integral value/ work = 0.2290      KE= .204

         work - KE = 0.2290-0.204 = .026  Although it does once again not equal 0 we can still assume that the work done = KE. The reason why it does not equal zero is probably because of an error with motion detector or an error when we calibrated our force or motion sensor. 

EXPT 2 Work Done by a Nonconstant Spring Force

For this experiment we used the same setup as last time but we made a few changes we connected the force sensor to a rod at the end of the table. Then we connected the spring to the cart and to the force sensor. After this we pulled the cart towards the motion sensor until the string was stretched for about .60 m. We tried to pull the cart at a constant rate. We then got the force vs position graph and got the spring constant from this. 

6.

In order to get the spring constant I used the following equation:

the integral gave us the work done. 

- work = 1/2 k x^2 

0.7068 N*m = 1/2 k (.5m)^2

k= 5.6544

EXPT 3:Kinetic Energy and The Work - Kinetic Energy Principle

I will have to redo this one because I forgot to find the KE at different positions.

EXPT 4: Work- KE theorem

For this experiment we have to watch a video, create a Force vs. Position graph , find the work that was done, and then find the kinetic energy and compare it to the work that was done. 

The work that we calculated should be equal to the kinetic energy however in this case they are not. This might be due to the fact that our graph wasn't completely accurate it was just a rough estimate. I believe this is the major reason why our work isn't equal to the kinetic energy.