Marble roller coaster -Kinetic energy

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Materials and Equipment


  1. Cut the foam pipe insulation in half (the long way) to make two U-shaped channels.
    1. The illustration below shows the foam pipe insulation, end-on.
      Foam pipe insulation is cut length-wise into two even halves
      Figure 1. The illustration above shows the cross-section at one end of the foam pipe insulation
    2. The insulation comes with one partial cut along the entire length. Complete this cut with the utility knife (yellow circle in the illustration above).
    3. Make a second cut on the other side of the tube (yellow line in the illustration above), along the entire length of the tube.
    4. You’ll end up with two separate U-channel foam pieces. You can use masking tape to attach pieces end-to-end to make the roller coaster track as long as you want.
  2. To make a roller coaster track, tape two (or more) lengths of the foam U-channel together, end-to-end. The joint between the two pieces should be as smooth as possible.
  3. You can make the track as simple or as complex as you’d like. You can add curves, loops, and additional uphill and downhill sections. The illustration below shows two examples. You’ll find that one requirement is that the starting point be the highest point on the track.
  4. In order to measure the velocity of the marble, you’ll need a way to measure how much distance the marble travels during a measured time interval.
    1. A good way to do this is to interrupt the foam track and direct the marble along a smooth, level surface (e.g., two long pieces of Masonite glued in a V-shape). Support the Masonite V (with cardboard, beanbags, etc.) so that it is level with the end of the foam track.
    2. Paint the Masonite with 5 or 10 cm long stripes in contrasting colors (e.g., red and white or black and white) so that you can use it to measure distances.
    3. Use the stopwatch to measure the time it takes for the marble to travel a certain length along the Masonite track.
    4. You can also videotape the marble, and use the measuring stick to measure the distance the marble travels in successive frames (each standard video frame is 1/30 second).
  5. Measure the height of the starting point for the track.
  6. Measure the mass of the marble.
  7. Calculate the gravitational potential energy of the marble at the starting point.
  8. Run a single marble down the track 10 separate times.
    1. For each run, use your striped measuring stick and stopwatch to measure the velocity of the marble as it completes the track.
    2. Calculate the average of your 10 measurements.
    3. More advanced students should also calculate the standard deviation.
  9. From your velocity measurement and the mass of the marble, calculate the kinetic energy of the marble.
  10. Repeat the velocity measurement at various points on the track by cutting the track and allowing the marble to continue on in a straight line on a smooth surface. Use your striped measuring stick and stopwatch to measure the velocity of the marble.
  11. Does the marble’s kinetic energy ever equal or exceed its initial gravitational potential energy?
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