Using Energy Skate Park to Study Energy Pie Charts

Energy Skate Park – Energy vs. Time Graphs

We will use “Energy Skate Park” to study energy vs. time graphs. The simulation assumes that everything is in the system. Open the program, “Energy Skate Park”. Construct a track with one valley – similar to the one on the right.

You will be using energy vs. time graphs to indicate how energy is distributed among the different storage modes. The storage modes are Ek (“Kinetic Energy), Eg (Gravitational “Potential Energy”) and Ediss (for “Thermal Energy”). Make sure that there is no friction present.

1. Sketch what you think the energy vs time graphs will look like for the skater at TL (top left), B (bottom) and TR (top right). Remember that when the skater reaches TR he will move back down the hill. To the right of the graphic (skate park hill), find the “Energy Graphs” section, and select “Energy vs. Time.” You are now ready to use the energy vs. time graphs to examine how energies change for the skater as he moves along the track.

Place the skater on the highest point of the track on the left, let him roll and watch what happens to the different energies in the bar graph. If the skater flies off the track, use the blue circles to adjust the track until the skater stays on all the way. If the changes are going too fast for you, use the slider under the graphic to adjust viewing speed between “slow” and “normal.” You can also use the “Pause” and “Step” buttons to the right of the slider to look at the bar graph for any given position along the track.

2. Complete the energy vs. time graphs below for the actual energies observed. How do your sketches compare to your predictions for each location?

Did your graphs overestimate any of the energy storage modes? Which one(s)?

Can you now explain how the results were different from what you expected?

If anyone in your group had a different explanation than you did, what was it, and how did your group resolve the difference?

4. On the bottom of the controls on the right (you may have to scroll down to find it), find and select the “track friction” button. With the slider all the way to the left, as it has been so far, friction between skater and track is zero. You will adjust the slider two notches to the right. Before you again run the simulation, describe what you think will be different about the graphs from the initial situation without friction.

Start the skater at the top left, and run the simulation.

5. How do your graphs compare to your predictions?

What happened to the amount of Eg and Ek as time went on? Why do you think this occurred?

What happened to the amount of Ediss as time went on? Why do you think this occurred?

6. Given what happens to the amount of Ediss as time passes, how is this different from what happened between the other modes of energy storage?

9. Does the total amount of energy stay the same? What can you conclude from this?

10. What do you think will happen to the amount of Eg stored in the system when the reference level is changed? Explain your reasoning. The reference level can be changed by checking the box in front of the right hand side menu option entitled Potential Energy Reference as shown below:

Now look at the bar graphs as the skater Dude moves across the track you constructed. Do the bar graphs match your predictions in question 10? If not, how so? Why do you think this is so?

11. What happens to the amount of energy stored in the system when the skater is lifted from the ground to some level on the track?

12. Make adjustments to your track, look for any variations from what you’ve seen so far and make notes about the differences. In particular what happens if the track is adjusted so that the skater flies off and hits the ground? Does this result make sense? Why or why not?