MECHANICAL POWER
 

In the examples shown by Fig. 1, the object acquires potential energy when it is lifted, and this potential energy is converted to kinetic energy as the object falls (if it is allowed to fall). The final burst of sound, shock waves, and perhaps outflying shrapnel is the last of the kinetic energy imparted to the object by lifting. Where does power fit into this scenario?

Fig. 1. Work is done when a force is applied over a specific distance. In this case, the force is applied upward to an object against Earth’s gravity.

A slight variation on this theme can be used to talk about power. This is shown by Fig. 2. Suppose that instead of a free end of rope, you have a winch that you can turn to raise the object at the other end of the rope. The object starts out sitting on the floor, and you crank the winch (or use a motor to crank it) for the purpose of lifting the object. This, possibly in conjunction with a complex pulley system, will be necessary if you have a heavy object to lift. Then the pulley had better be strong! The same holds true for the rope. And let’s not forget about the manner in which the pulley is anchored to the ceiling.

Fig. 2. Illustration of power. A winch and pulley can be used to life a heavy object.