Question

When the speed of a front wheel drive car is increasing on a horizontal road, the direction of the frictional force on the tires is:
(A) forward for all tires.
(B) backward for all tires.
(C) forward for the front tires and backward for the rear tires.
(D) backward for the front tires and forward for the rear tires.

Answer 1

Hint: The direction of the frictional force is always opposite to the motion of the object, so use this concept for the determination of the correct answer.

Complete step by step answer:
Whenever an object moves on the surface of the ground, the frictional force comes into the action and always acts in the opposite direction of the motion. The magnitude of the frictional force depends on the roughness present on the surface of the ground, and it can influence the moving condition of the object. A large amount of frictional force tends to stop the motion of the object very fast compared to the small amount of frictional force.

In case of the motion of the car, if the speed of a front-wheel drive car is increasing on a horizontal surface then in this condition the rolling motion of the rear tires is in the backward direction against the ground. So, for the backward direction motion, the frictional force acts on the rear tires in the forward direction. On the other side, the front tires roll due to the effect of frictional force, so to move the front tires in the forward direction, the direction of the frictional force must be in the backward direction.

So, the correct answer is “Option D”.
That is backward for the front tires and forward for the rear tires.

Note:
The direction of the frictional force acting on the rear tires must be opposite to the direction of the frictional force acting on the front tires.Also The front wheels push the ground backwards thus getting a forward frictional force and for the rear wheels the frictional force is the driving force for its rolling which is in backward direction.