Answer to Question #144234 in Mechanics | Relativity for Mikkos Joshua Garcia

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. What are the coefficients of static and kinetic friction?
b. Based on your answer in e, which is greater – coefficient of kinetic friction or coefficient of static friction?
c. Is it easier to start the crate moving or to keep the crate moving? Explain.

Answer 1

Weight of the crate is 500 N.

Force required to start the crate to move is 230N.

Let coefficient of static friction is $\mu_s$

Then, $\mu_s = 230/500 = 0.46$

Force required to move with constant velocity is 200N.

Then coefficient of kinetic friction is given by, $\mu_k =200/500=0.4$

From the calculation, it is clear that coefficient of static friction is greater than coefficient of kinetic friction.

It is not easy to give motion in crate rather than moving crate at constant velocity because we need more force to give motion to the crate than moving it with constant velocity.