A heavy box is in the back of a truck. the truck is accelerating to the right. apply your analysis to the box. a) draw a motion diagramb) draw a force identification diagramc) draw a free body diagram

From the motion diagram, we can see that the box accelerate in the same direction with the truck (to the right). We can recall from Newton's second law of motion that the acceleration of a body as produced by the net force is directly proportional to the net force in the same direction and inversely proportional to the mass of the body (F = ma), there must be a force acting to the right one the box to prevent it from sliding against the truck. This is fictional force which is static frictional force. If not for this static friction between the box and surface on the truck which it is placed, the box will slip off the back of the truck but the friction act in the direction needed to prevent slipping. In this case the frictional force act in the same direction as that which the truck is accelerating.

It is given that, a heavy box is in the back of a truck and the truck is accelerating to the right.

The description is shown in figure 1. Here, the forces that act on both box and the truck are the normal force, the frictional force and their weight mg.

The free body diagram is shown in figure 2. This shows the total forces (F = ma) acting on the truck. As a result, the truck will move in a forward direction.

Hence, this is the required explanation.