Question

1. You are trying to move a 500-N crate across a level floor. To start the crate moving, you have to pull with a 230-N horizontal force. Once the crate "breaks loose" and starts to move, you can keep it moving at constant velocity with only 200-N.
a. Draw a free-body diagram for crate just before it starts to move.
b. What forces are acting on the crate just before it starts to move?

Answer 1

Answer

a. Free body diagram can be drawn as

b. There are static coefficient of friction

Will be

$\mu_s=\frac{230}{500}=0.46$

Kinetic coefficient of friction will be

$\mu_k=\frac{200}{500}=0.40$

Force on the block just before it star to move.

In forward direction F=200N

In backward direction due to friction

f=200N

Vertically upward Normal reaction N=500N

Vertically downward W=mg=500N

Block is moving with constant velociy so there are no any acceleration so appalied force will be equal to kinetic friction.