We apply the work-energy theorem, the conservation of mechanical energy, and its relation with internal energy, in order to solve our problem which is about a moving car. The car starts from rest under the action of the traction force. It reaches point A with a speed of 72 km/h. When the car reaches point A, the driver removes his foot from the accelerator pedal and he applies the brakes, so the car reaches point B, 50 m away from A, with a speed of 10 m/s. The traction force becomes zero.
At point B, the driver removes his foot from the brake pedal, and the car continues its motion along the inclined plane BCD which makes an angle of 30^o with the horizontal.
Suppose that the traction force remains zero.
We neglect air resistance and the mass of the fuel.
You can watch:
1) Mechanical energy – 2 solved problems :
2) Mechanical energy – Solved problem 1 :
3) Internal energy :
4) Conserved and nonconserved mechanical energy :
5) Gravitational potential energy :

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