A horizontal shove of at least 200-N is required to start moving an 800-N crate initially at rest on a horizontal floor.The coefficient of static friction is:
A)0.125
B)0.25
C)0.50
D)4.00
E)none of these

Question

Quizplus · Accepted Answer

The equation for static friction is:

fs ≤ μs N

where fs is the force of static friction, μs is the coefficient of static friction, and N is the normal force (equal to the weight of the crate in this case, which is 800 N).

To start moving the crate, the applied force must be greater than or equal to the force of static friction:

Fapp ≥ fs

From the problem, we know that Fapp = 200 N. So, we can rearrange the inequality to solve for μs:

μs ≤ Fapp/N

μs ≤ 200 N / 800 N

μs ≤ 0.25

Therefore, the coefficient of static friction is 0.25, which corresponds to choice B.

A Horizontal Shove of at Least 200-N Is Required to Start