Stop in the Zone
The server picks a track, cart mass, gravity and friction, plus a target zone for how far the cart rolls in total before it stops (always achievable), you dial in the release height, and real energy-on-a-track physics judges the run. Stopping in the zone refunds your run.
About this simulation
What it shows
A puzzle on a cart rolling on a curved track with friction: the track, the cart's mass, gravity and friction are given, along with a zone for the total distance the cart rolls before it stops. You choose the release height, then run it.
The key idea
Friction turns some of the cart's energy into heat on every metre it rolls, so it stops once all its starting energy is used up. A higher release height means more energy to use up, so the cart rolls farther in total.
Try this
Run it once at the starting height and see whether the cart stops short of the zone or goes past it, then raise or lower the Release height slider until it stops inside the zone.