Question

The 75-kg man pushes on the 150-kg crate with a horizontal force F. The coefficients of static and kinetic friction between the crate and the surface are μs = 0.3 and μk = 0.1, and the coefficient of static friction between the man's shoes and the surface is μ′s = 0.8. What is the greatest acceleration the man can give the crate if the man's acceleration is zero at this instant?

I keep getting 1.96 but it says answer is incorrect..

Answer 1

For the man

Maximum force that the man can apply is

For the crate

Minimum force needed to start the crate

The man is applying a larger force, so the crate will move.

Now the kinetic frictional force on the crate is

Greatest acceleration of the crate