A car is driven at 80km/h on a horizontal road. If the car is now driven up 10m high rise, what speed would it have at the top of the rise? ( Assume thet the wheels of the car roll at all times so thatit dosen't experience sliding friction ; exclude any other dissipative forces )

Answer 1

Neglect air and tire friction and assume conservation of mechanical energy. Convert V1 (the initial velocity) from 80 km/h to meters/second. You have to assume that the car is "in neutral" so that the engine is not continuing to provide power. They should have told you that. Most cars continue to provide some power even when the foot is off the gas, so that the engine does not die.

(1/2)M (V1^2 - V2^2) = M g H
Solve for the final velocity V2. Note that M cancels out. H = 10 meters