posted by Tasha .
85 lb force is applied to the 200lb crate, which is stationary before the force is applied. Determine the force exerted by the horizontal surface on the crate
Assuming the crate is on a horizontal surface, so gravity is dedicated to the normal reaction N = 200 lb. force, and the 85 lb.force applied is used to overcome the static friction offered by the horizontal surface.
Therefore the (resistive) force exerted by the horizontal surface is equal to the applied force of 85 lb. force.
We have assumed that after the force is applied, the crate either remains stationary or moves with a uniform velocity.