1. The problem statement, all variables and given/known data A car is moving on a horizontal road with speed of 60 km/h. When it starts to move on an inclined plane its velocity decreases by 10 km/h. How much its velocity will increase when the car starts to move down the plane? Assume that the power of the engine remain the same, any friction is neglectable. 2. Relevant equations Newton's Laws of Motion 3. The attempt at a solution The correct answer is 15 km\h. I don't understand this. Please help.