A force of 36.1 N is required to start a 4.0 -kg box moving across a horizontal concrete floor. If the 36.1 N force continues, the box accelerates at 0.71 m/s^2. What is the coefficient of kinetic friction?

Answer 1

netforce=mass*acceleration
36.1-mu*mass*g=mass*acceleration
solve for mu.

Answer 2

I got 0.072 as my answer and this is showing as in correct.

I did:

36.1 - mu x 4.0kg x 9.8 = 4.0kg x 0.71

0.71 / 9.8 = 0.072