A driver sets his cars cruise control on a flat highway, causing the car to travel at a constant velocity. Which is true in this situation?

Question

Responses
A The cruise control decreases friction.The cruise control decreases friction.
B The cruise control causes the car to experience an unbalanced force.The cruise control causes the car to experience an unbalanced force.
C The force from the driver's foot is needed to keep the car from stopping.The force from the driver's foot is needed to keep the car from stopping.
D The force of friction is balanced out by the forward force applied by the engine.

Answer 1

The correct response is:

D The force of friction is balanced out by the forward force applied by the engine.

In this situation, the cruise control system maintains a constant velocity by ensuring that the force produced by the engine (thrust) is equal to the force of friction (and any other opposing forces like air resistance). Since the car is traveling at a constant velocity, according to Newton's first law, the net force acting on the car is zero, meaning the forces are balanced.