# 18.2: Introduction


When lifting weights at the gym, you use energy to move the weights.  Mechanical work occurs when energy is used to move an object a distance.  Mechanical work and energy have the same units of Joules, which indicates that they are closely related.  The use of energy does not always result in mechanical work; an object must be moved for there to be mechanical work done on an object.

$W = Fd \nonumber$