Conservation of mechanical energy – kinetic and potential energy on a track
Integrated ScienceEnergyAges 14–15
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Energy
A ball slides on a bowl-shaped track or a ramp joined to a flat section. Drag the ball to a starting height and release it: the kinetic energy bar Ek = ½mv² and the potential energy bar Ep = mgh trade off while total mechanical energy stays constant with no friction; turning friction on shows energy converting into heat. An energy-vs-time graph, the work done by gravity, and the power all update continuously.
Lesson: Kinetic and potential energy; mechanical energy; work and power
What it shows
A ball moving on a track exchanges gravitational potential energy Ep = mgh and kinetic energy Ek = ½mv². Without friction only gravity does work, so the mechanical energy E = Ep + Ek stays constant: the ball rises to its starting height on the other side, and its speed at the lowest point is v = √(2gh), whatever its mass. With a friction coefficient μ above zero, some mechanical energy becomes thermal energy Q on every pass, so the ball rises less each time and finally stops. The model uses g = 10 m/s².
How to use
Drag the ball to a starting height and press Release ball. Pause near the top and the bottom of the track and compare the Ep and Ek bars with the values in the equation line. With μ = 0, check that E stays equal to E₀; then increase μ and watch the heat Q grow while the energy-vs-time graph shows E falling. Change the mass or the track shape and compare the speed at the lowest point.
Parameters you can change
- Ball mass 0.1–5 kg
- Starting release height 0.5–5 m
- Friction coefficient μ 0–0.5
- Track shape Bowl-shaped track (dips on both sides), Ramp joined to a flat section
- Show energy-vs-time graph
Questions to explore
- At which point on the track is kinetic energy greatest and potential energy smallest?
- Released from 2 m without friction, how fast is the ball at the bottom? Does this depend on its mass?
- When friction is present, what form of energy does the lost mechanical energy become?
