ENERGY  I

In this part of the lab, you will do some qualitative investigations of energy to practice with the concepts of kinetic and potential energy. There are no calculations in this part just thinking. Therefore, you need to write good descriptions of your thoughts in your notebook. Do not allow the cart to crash off the end of the track during your experiments!

• Elevate the track so that the end without the bumper is higher than the other end.
• The cart has a spring in one end which can be compressed and held at three different positions. Compress the spring to the maximum possible extent and set the spring end of the cart against the bumper.
• Release the spring by tapping on the release mechanism. (Using the eraser end of a pencil or a ruler works better than using your hand. Be sure to press straight down so that you don't give the cart an extra shove to the left or right.) Describe what happens.
• Estimate the distance traveled to the highest point in the motion.
• Experiment with the track set to different angles - i.e. different elevations of the track

What is the nature of the relationship between the angle of the track and the distance traveled? Explain your results in terms of energy.

Set the angle of the track such that the cart travels more than half of the track for the greatest spring compression. Keep this height constant for the remainder of the experiment.

• Make a note of how far up the track the cart goes.
• Repeat the experiment with the other two compression distances.
• Explain your results in terms of energy.
• Now using the greatest compression available, try different amounts of mass on the cart.
• Describe what you observe.
• Again, explain your results in terms of energy.

The next portion is quantitative where we will have Logger Pro make measurements using the Lab Pro.

• Set the sonic ranger near the raised end of the track.
• Using the cart without any extra mass and the greatest compression, make distance, velocity and acceleration graphs.
• Release the cart once you hear the sonic ranger start 'chirping'.
• Print your graphs and include them in your report.
• Think about your graphs in detail.
  • Is the behavior of the graphs as you would have expected?
  • Explain what is happening in each part of the three motion graphs.
  • Why is the second acceleration peak greater in magnitude than the first one?

Now that you have data you need to use Logger Pro™ to calculate the KE, PEg and ME of the cart. KE is pretty straightforward, but what about PEg?  You measured the position as a function of time, but you need the height in order to find PEg.  The inclination of the track is constant.  The tangent of the inclination is the ratio of the height of your spacer to the separation between the legs of the ram (assuming you placed your elevating block under the feet).  Is the energy of the cart conserved? What evidence do you have to support your answer? If it is not conserved, where does the lost energy go?

Describe any other interesting physics you noticed in this experiment that was not covered in answering the above questions.