Does gravity affect the speed of a car moving in a straight line?

1 Answer
Jan 28, 2016

When a car continues to move in a (locally) horizontal road, the gravitational force is normal to the road. Speed is not affected. When the road is rising/falling, there is retardation/acceleration.

Explanation:

The resultant of the normal (upward vertical) reactions of the horizontal road on the wheels balances the (downward) gravitational force called weight of the car. So, there is no contribution of gravity to the horizontal speed..