posted by Seth .
A box of books weighing 290 N is shoved across the floor of an apartment by a force of 400 N exerted downward at an angle of 35.0° below the horizontal. If the coefficient of kinetic friction between box and floor is 0.57, how long does it take to move the box 3.80 m, starting from rest?
Calculate the acceleration rate, a, using Newton's second law:
Fnet = M a
Then get the required time t using
3.80 m = (a/2) t^2
The net force Fnet is the difference between 400 N and the friction force.