A 25-kg box slides, from rest, down a 9.0-m-long incline that makes an angle of
15° with the horizontal. The speed of the box when it reaches the bottom of the
Incline is 2.4 m/s.
(a) What is the coefficient of kinetic friction between the box
And the surface of the incline?
(b) How much work is done on the box by the
Force of friction?
(c) What is the change in the potential energy of the box? :confused:

1. Have a sketch, on which you draw the forces acting on the box.

a) Find the force acting on the box, perpendicular to the slope. (use trigonometry)
Find the acceleration of the box with friction using the motion formula (Initial speed u is zero)
Find the force on the box, with friction.
Subtract the actual force from the estimated force without friction, to get the force due to friction.


b) Work = Force due to friction x Displacement

c) Potential Energy = Mass x Acceleration due to gravity x Height