Answer to Question #157332 in Physics for Elaina

Question

 Starting at the top of the hill, Eric rides his mountain bike down to the bottom of the hill. Friction acts on him the entire time. What can be known about his mechanical energy?

Answer 1

Potential energy decreases and is converted into kinetic energy. Part of the mechanical energy is converted into heat due to the action of friction.

$mgh=mv^2/2+A_{fr}$ ,

where $A_{fr}$ is the work of friction forces. At the bottom of the hill $PE=0.$