Question

Matt, in the foreground of Fig. 4-39, is able to move the large truck because

(a) he is stronger than the truck.

(b) he is heavier in some respect than the truck.

(c) he exerts a greater force on the truck than the truck exerts on him.

(d) the ground exerts greater friction on Matt than it does on the truck.

(e) the truck offers no resistance because its brakes are off.

Short answer

The correct option is (d).

Step-by-step solution

Step 1. Action of various forces on Matt and the truck

Given data:

If the truck and Math both want to move forward, the friction force acts in the backward directionon both of them.

The forward force on Matt is equal to the force of friction on Matt.

The backward force on Matt is the tension of the cable between Matt and the truck.

Assumption:

Let the force on Matt by the truck and the force on the truck by Matt be the tension force on the cable.

Step 2. Condition to move the truck

When the truck is not moving, the cable's tension is equal to the friction force acting on the truck.

When the large truck moves, the tension is greater than the force of friction on the truck.

Also, this time Matt is moving, and the force on Matt is greater than the cable's tension.

Therefore, the ground exerts a greater friction force on Matt than it does on the truck.