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Lesson 4 Gravitational and Potential Energy

  Virtual Lab

Energy Skate Park © 2017 PhET
Work through this simulation activity to reinforce what you learned about mechanical energy, gravitational potential energy, and kinetic energy in a system.

You will manipulate a skate boarder at a skate park to investigate energy conversions that occur in a mechanical system.



  1. Click on the play button to open the activity. This activity can also be accessed at https://quick.adlc.ca/skatepark Click on “Intro.”
  2. Click on “Bar Graph.” Place the skater at the top of the left side of the track. Watch as the skater moves across the track and how it changes the levels of potential and kinetic energy. (You can slow or pause the skater down at the bottom of the simulator window to help you observe).
  1. When is the gravitational potential energy the highest?

    When the skater is at the top of either side of the track.
    The lowest?

    When the skater is at the bottom of the track.
  1. When is the kinetic energy the highest?

    When the skater is at the bottom of the track.
    The lowest?

    When the skater is at the top of either side of the track.
  1. When are the kinetic and gravitational potential energy levels the same?

    When the skater is halfway through the path on either side of the track.
  2. What do you observe about the total energy value? (This is the mechanical energy of the system).

    The total (mechanical) energy does not change through the movement of the skater.
  3. Place the skater halfway down on the left side of the track. Watch as the skater moves across the track and how it changes the levels of potential and kinetic energy at this new starting height.

  4. How did the total energy value change when you moved the skater to the new starting point?

    The total (mechanical) energy has decreased with the movement of the skater.
  5. Click on “Speed.” Place the skater at the top of the left side of the track. Watch as the skater moves across the track and how it changes the levels of potential and kinetic energy and also the speed. (You can slow or pause the skater down at the bottom of the simulator window to help you observe).

  1. When is the speed the highest?

    When the skater is at the bottom of the track.
    The lowest?

    When the skater is at the top of either side of the track.
  2. Move “Mass” to “Small.”
  3. What do you observe about the total energy value? (This is the mechanical energy of the system).

    The total (mechanical) energy still does not change through the movement of the skater, but it has an overall smaller value.
  4. Move “Mass” to “Large.”
  5. What do you observe about the total energy value? (This is the mechanical energy of the system).

    The total (mechanical) energy still does not change through the movement of the skater, but it has an overall larger value.
  6. Please return to the top of this page and click on analysis to complete the analysis questions.
  1. Can you think of a scenario when the kinetic and gravitational potential energy of the skater could both be zero? Explain.

    Kinetic energy is energy of motion, so the only time a skater’s kinetic energy is zero is when it is not moving.

    Gravitational potential energy is energy of position relative to Earth’s surface, so Ep can be zero if it is on the surface of Earth.

    If the skater stops moving, or falls, and lies at the bottom of the track, then the skater’s kinetic and gravitational potential energy could both be zero.

  2. Use the law of conservation of energy to explain how you can predict the height that the skater will reach on the right side depending on where you release them on the left side.

    The skater will reach the same height on the right side as the height she was released on the left side. This is because as the skater’s kinetic and gravitational potential energies are being converted back and forth, energy is not created nor destroyed.