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Work and Energy Reilly Bucy 4/7/2014 Physics 201 TA: Milad Haddadi Section: #17

This experiment involved a metal track, rolling cart, a weighted string attached to the cart, and a smart pulley sensor. The metal track was positioned at 0o or 60o and the cart and pulley were used to test the relation of work and energy on a flat or inclined slope. To test this relation a weight was applied to the cart and these results were compared to the results of no weight applied to the cart. The data of the experiment was collected through Datastudio and is shown on graphs representing work and energy vs. time.

Introduction: The report Work and Energy involves the ratio of work to energy and the relation of potential energy to kinetic energy. Kinetic energy is the energy an object has through motion, the energy of an object is defined by the equation

. This kinetic energy is translated from

potential energy which is the energy an object holds while at rest. The conditions under which the sum of the potential and kinetic energy should remain constant is under the absence of frictional forces on the object. In this case the frictional forces of the cart must be canceled which is achieved by applying paperclips to the string attached to the cart on the pulley. We can ensure the forces have been cancelled once the cart moves along the level track at a constant velocity. If the cart appears to increase velocity after a slight push there is too much weight attached to the pulley, if it slows down or stops there is too little weight. This procedure can ensure that the correct conditions are met and allow the experiment to be carried out smoothly. Experiment: The experiment was set up by leveling the track to the ground which would allow the correct cancelation of frictional forces. If an angle needed to be applied to the track a wooden block would be placed underneath to meet the specified angle. At the end of the track hanging over the edge of the table the smart pulley was positioned in order to hold the string with the attached weight. The hanging string held weight in the form of paperclips in order to cancel frictional forces. Once the forces are canceled a 20g weight was added at the end of the string. At the other end of the track the cart was positioned in order to roll across the track at a constant velocity. A small diagram of the experimental setup is shown below.

The program DataStudio was used to measure and calculate the Kinetic energy and work from the speed of the cart by the attached string. The program was able to perform these calculations from the programmed equations of work and KE. These equations included . Results: During this experiment it is expected that the KE remains similar to the work as the change of the final and initial kinetic energy is equal to the work of the system. But with the added weight at the end of the string the work may not equal the change of the KE. The reason for this is the added weight at the end of the string which would increase the kinetic energy of the cart. Below is a drawn graph of the experiment.

Conclusion: In conclusion the KE of the object is equal to the work done on the object when frictional forces are cancelled. But as seen in the experiment the addition of other forces shows this relation is only true in certain cases. An example of this is the conservation of energy, the conservative force of this experiment is gravity as it is cancelled by the paper clips, but the added 20g weight affects the ratio of work to kinetic energy. Acknowledgements: I would like to thank my lab partner for help throughout this experiment and in the lab work.