2. according to newton’s first law, if no force acts on an object, it will just continue moving. explain in terms of newton’s first law why a car engine must exert a force between the car and the road to drive at a constant speed on a straight and level road.

See below.

Explanation:

There is  a force acting against the car. This is the friction between the tyres and the road.  So there is a force acting on the car and Newtons First law only applies when there is no force acting on it. The car must then exert a force to overcome the friction in order to move at a constant speed.

higher potential

explanation:

because it is in a high speed so it must move into a of high potential