More problems....?

Question

a 12kg box is released from the top of an incline that is 5.0m long and makes an angle of 40deg. to the horizontal. a 60-N friction force impedes the motion of the box.

A. what is the acceleration of the box?

B. how long will it take to reach at the bottom of the incline?

Answer 1

Component of weight down the incline = mg sin(40) = 77 N.

Component F of resultant force  on box down incline = 77 - 60 = 17 N

Acceleration down incline = F/m = 1.43 m/s^2

Displacement = 5 m = 1/2 x 1.43 x t^2  

So t = 2.64 seconds.