The force of static friction exerted on an automobile's tires by the ground
A) provides the accelerating force that makes the car move forward.
B) does positive work on the car while it is accelerating.
C) does negative work on the car while it is decelerating.
D) does everything listed in (a), (b) and (c).
E) only does positive or negative work as in (b) or (c).

Question

Quizplus · Accepted Answer

The force of static friction between the automobile's tires and the ground is what allows the car to push against the ground and move forward. This frictional force does not do work on the car because it does not act through a distance (in the frame of the car moving forward). Work is defined as force applied over a distance, and since the point of application of the static friction force (the contact point between the tires and the ground) does not move relative to the car, it does not do work on the car.

The Force of Static Friction Exerted on an Automobile's Tires