Something I don’t quite understand from a physics standpoint. Imagine a car going down a road approaching a roundabout, on neutral; it can follow the roundabout 180 degrees and start going in the reverse direction while only losing a little speed/energy. But the car did a lot of “work” in the physics sense — a multi-thousand-pound vehicle completely reversed direction in a few seconds. How is that energy redistributed (force diagram, etc) to show where the energy for all that work came from?
In: 5
The energy stored in the car = the mass of the car times it’s speed
The energy got there by burning fuel or rolling down a hill
Coasting around a roundabout in neutral changes the direction of the car
The tyre’s warm up as they respond to the turn due to the friction of the road
The amount of heat generated in the tyres is a tiny fraction of the total energy stored in the moving car.
TL;DR It might look like the car changed direction without using energy but it did cost a tiny bit of momentum in that the tyres warmed up due to friction
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