Some systems are more stable than others. A pencil in stable equilibrium is less stable than a ball at the bottom of a bowl because it doesn’t take much of a displacement of the pencil to have the center of gravity outside of the stable point and to cause tipping of the ball. Stability in a person will involve lowering the center of gravity by crouching, which will be resistive of movement that tips the person over. Increasing the base of support will also increase the stability of a person or any system that needs to resist torque forces.
SIMPLE MACHINES Simple machines will multiply or augment a force that is applied to a system. Examples of simple machines include levers, pulleys, gears, screws, and wedges. Energy, as always, is conserved, and a machine cannot do more work than the energy put into it. Machines, on the other hand, are able to reduce the input forces necessary to do the specific job it does. The mechanical advantage of a simple machine is equal to the Force output divided by the Force input. Figure 48 shows an example of a lever, which is a simple machine:
Figure 48.
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