Question

A truck is traveling horizontally to the right (Fig.4–38). When the truck starts to slow down, the crate on the (frictionless) truck bed starts to slide. In what direction could the net force be on the crate?(a) No direction. The net force is zero.(b) Straight down (because of gravity).(c) Straight up (the normal force).(d) Horizontal and to the right.(e) Horizontal and to the left.

Short answer

The obtained result is option (a) that states: No direction. The net force is zero.

Step-by-step solution

Step 1. Determine the magnitude of the force on the crate  

In this problem, one of the essential points is that the total force on the crate will not act in the vertical direction when the crate does not accelerate either up or down.

Since the bed of the truck is frictionless and there is no other surface in contact with the crate, the horizontal force acting on the crate will be zero.

Step 2. Determine the direction of the force on the crate

As mentioned above, there is no net force exerted on the crate because both horizontal and vertical forces are of zero magnitude. So, the force on the crate will have no direction.

Thus, option (a) is the correct answer.