MOVEMENT ANALOGY

� GEARS

Gears are wheels with teeth around their edges. The teeth fit together so that when one gear turns, its teeth push against another gear�s teeth, causing it to turn as well. Gears that are next to each other rotate in opposite directions.

How do gears make life easier?

When a smaller gear drives a larger gear, the larger gear turns with more force. This is force magnification. Lower gears on a bike allow you to apply more force with each turn of the pedals, though you have to pedal more often! When a larger gear drives a smaller gear, the smaller gear completes its turns faster. The gears are magnifying a movement. When you turn the large gear in egg whisks, it causes smaller gears to spin four times as quickly. This is fast enough to turn egg whites into foam! When a series of gears are joined together, they can transfer motion energy across the whole series.

� PULLEYS

A pulley is a wheel that turns on an axle.� An example of a pulley is a flagpole.� Some amusement park rides are examples of pulleys.� There are different types of pulleys such as a fixed pulley or a pulley that stays in the same place.� With a fixed pulley, you change the direction of force, not the force needed.� Then there�s a moveable pulley.�