Energy Dissipation
From the Drag Force section, we learned that
friction causes the balls on the table that are sliding to slow down. This means
that the kinetic energy of the balls decrease and eventually to zero when the
balls come to rest. With zero external force on the pool table, the energy of
the system must be conserved. Then, what happened to the kinetic energy? Kinetic
energy has been dissipated through friction.
This energy dissipation is mathematically expressed as:
Etherm = fkDx
Dx is the displacement of the object.
Energy dissipation through friction is also called the thermodynamic energy
dissipation, because when two surfaces rub against each other, heat is created.
Now including this frictional dissipation, the energy equation to describe the
pool system becomes:
(1/2)mvi2 = fkDx
Sample Problem
The cue is initially traveling at 10 m/s. If the mk
= 0.25 between the tablecloth and the surface of the ball, and the cue was 8 meters away
from the rail, will it hit the rail before coming to rest?