Work done by Friction

1. Oct 13, 2004

Hughey85

Hi everyone. I have another problem that is just stumping me. I posted this earlier and still can't understand it. Here it is...

A 1-kg ball starting at h = 6.1 meters slides down a smooth surface where it encounters a rough surface and is brought to rest at B, a distance 18.3 meters away. To the nearest joule what is the work done by friction?

Imagine the ball starting on top of a waterslide, sliding down with no friction, and then coming down onto the straight path that slows you down. I can find the Potential Energy of the ball, but don't know where to go from there! Pls help!

2. Oct 13, 2004

Leong

Law of conservation of energy :
Total energy in the beginning=Total energy in the end
$$mgh= W_f$$
The potential energy of the ball has been transformed to heat etc due to the work done by friction.