Kinetic and Potential Energy Simulation

Energy is never lost, only changed from one kind to another. A skater high on a track has stored (potential) energy, m g h, which depends on mass, gravity and height. As it rolls down, that turns into movement (kinetic) energy, ½ m v², so it speeds up; climbing the other side turns it back. With no friction the two always add up to the same total, so a skater released from height h reaches a speed of v = √(2gh) at the bottom whatever the shape of the track, and whatever its mass, because the mass cancels. Friction turns some of the energy into thermal energy (heat), so the skater climbs a little less each time and finally stops, but the total, counting the heat, is still exactly what it started with. This model slides the skater as a point on the track, with no rolling and no air resistance, and keeps it on the track like a roller coaster. Students can change mass and gravity and compare what happens. Use it for physics inquiry with Grade 5, Middle School, and High School on a projector or student device.

• Drag the skater to different heights and see how the speed at the bottom changes
• Slide the mass up and down: the bars change size but the ride stays exactly the same
• Switch between the Moon, Earth and Jupiter and compare the speed at the bottom
• Add a little friction and watch the thermal bar grow while the total stays the same
• Try the three tracks and find out whether the shape changes the speed at the bottom
• On the hills track, find the lowest start that still gets the skater over the hill

1. 1Predict how changing mass will affect the speed at the bottom, then test the prediction.
2. 2Use evidence from the live calculation and visual to explain the result.

Questions teachers ask