"Let's Learn about Potential and Kinetic Energy!" Potential energy exists whenever an object which has mass has a position within a force field. The most everyday example of this is the position of objects in the earth's gravitational field.

The potential energy of an object in this case is given by the relation:

PE = mgh where

  • PE = Energy (in Joules)
  • m = mass (in kilograms)
  • g = gravitational acceleration of the earth (9.8 m/sec2)
  • h = height above earth's surface (in meters)

    • Kinetic Energy exists whenever an object which has mass is in motion with some velocity . Everything you see moving about has kinetic energy.

    The kinetic energy of an object in this case is given by the relation: KE = (1/2)mv2 where

  • KE = Energy (in Joules)
  • m = mass (in kilograms)
  • v = velocity (in meters/sec)
    •  This principle asserts that in a closed system energy is conserved. This principle will be tested by you, using the experimental apparatus below. In the case of an object in free fall. When the object is at rest at some height, h, then all of its energy is PE.

    As the object falls and accelerates due to the earth's gravity , PE is converted into KE. When the object strikes the ground, h=0 so that PE=0, the all of the energy has to be in the form of KE and the object is moving it at its maximum velocity. (In this case we are ignoring air resistance).

    This appartus will drop a mass from different heights. When the mass strikes the ground, some percentage of its original energy will be absorbed by the ground.

  • The Total Energy (Energy)
  • The mass of the object (Mass)
  • The percentage of the energy which is absorbed by the surface on each "bounce" (EAS)

    • In addition you can measure the height of the object above the surface by clicking on the black platform upon which the object rests. The impact velocity of the object will also be given at each bounce.

    The functionality of the buttons are as follows:

  • Start= Drop the ball after Energy, Mass and EAS have been set; resume after step or pause has been selected
  • Step = Drop the ball once and it rebounds to its maximum height and then pauses
  • Reset = Reset experiment to intial values
  • Pause = Pause the animation at any point
    • Initial Values:
  • Select a Mass of 5 KG
  • Select an Energy of 200 J
  • Select EAS = 50%
    •

    Questions to think about first:

  • What is the height of the ball? (verify by measuring it)
  • How high will the ball bounce on the first bounce (verify by selecting step and then measuring the height)
  • What will be the impact velocity of the ball on the first bounce

    • Experimental Steps:

  • Activate the step button to run the experiment and check your answers to the three questions above.
  • Reset the experiment and set EAS to 100%. What do you expect will happen?
  • Reset the experiment and set EAS to 25%. What will be the height of the ball on the first bounce?
  • Reset the experiment and set Energy to 400 and answer the question 1-3 above again.
  • Reset the experiment and change the mass of the ball to 2 kg. How much higher did the ball rise? Will the ball have a different velocity on initial impact as in the previous case? If so, how come? If not, why not?
  • Which combination of parameters do you think will allow the ball to bounce the most number of times? Try your guesses
  • Which combinations of parameters produces the lowest and highest initial heights? Try your guesses.
    • I desire to to have the impact velocity be 6 meters/second on the third bounce Bonus Question: What combination of Energy, M and EAS will satisfy Issac? Try to work it out in advance.