"A 10.0 kg box is held at the top of a 12.0 m long delivery ramp that makes a 17.0 degree angle with the horizontal. When the box is released, it slides down the ramp, with a constant 20.0 N frictional force exerted on it over the full 12.0 m . What kinetic energy does the box have at the bottom of the ramp

Explanation:

work done by gravitational force

mgsinθ x d  , m is mass of box , θ is angle if inclination , d is displacement

= 10 x 9.8 x sin17 x 12

= 343.83 J

this work will be positive

work done by frictional force

= force x displacement

20 x 12

= 240 J

this work will be negative

net positive work done on box

= 343.83 J - 240 J

= 103.83 J

This work will be converted into kinetic energy .

So kinetic energy of box at the bottom of ramp

= 103.83 J .