Question

39. Draw a complete free body diagram of a 40 kg plastic crate at rest on a wooden table (us=0.7). The applied force to the right (and horizontal) is 9 N. Label all forces acting on the crate along with the magnitude of the forces.

Answer 1

In order to draw the free body diagram, first let's calculate the friction force acting on the crate:

$\begin{gathered} F_f=N\cdot\mu \\ F_f=40\cdot9.8\cdot0.7 \\ F_f=274.4\text{ N} \end{gathered}$

Since the friction force is greater than the force applied, the crate will not move, and the friction force will be equal to the force applied.

The weight force is equal to 40 * 9.8 = 392 N.

So, drawing the diagram, we have: