Question

The thrust from a car is 590 N. The air resistance and friction together total 680 N. What happens to the speed of the car?

Answer 1

The net force in the direction the car is traveling (forward) is

(590 - 680) = -90N = 90 newtons backwards.

The car accelerates backwards at the rate of (90/its mass) m/sec-squared.

Another way to look at it: The car's forward speed decreases at that rate.