Teaching Physics with the Physics Suite

Edward F. Redish

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Energy-Skate Park 2

In the figure at the right is shown a simulation of a skateboarder sliding along a curved track. The dotted line at the bottom of the track shows where we have taken the zero of the gravitational potential energy. Seven points along the track are marked with small circles (labeled A – G). The skateboarder starts at rest at the point labeled A. He then starts rolling down the track. For this problem, ignore friction and the rolling effects of the (small) wheels.

A) In the figure at the right is shown a bar graph representing the division of energies at one of the labeled points. Which point do you think it is? Justify your answer.

B) In the figure below is shown a plot of the skateboarder’s various energies as a function of time. Where is he on the track at t = 0 s, 2.9 s, 5.3 s, and 6.9 s? (These times are marked by arrows below the graph.)

C) The skateboarder and his skateboard together have a mass of 75 kg. If he is traveling at 2 m/s when he is at point C, 3.3 meters above the lowest point on the track, how high is point A above the lowest point on the track?

Page last modified November 7, 2010: PE36