1 minute read
Simple Machines
by AudioLearn
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
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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.
Figure 49 shows forces on a fulcrum that has a mechanical advantage on the lifting of a weight. This uses torque acting at a distance on a heavy object opposite the fulcrum:
Figure 49.
In such cases, the length input times the Force input equals the length output times the force output. What this means is that the ratio of the force output and the force input is inversely proportional to the length input divided by the length output. The further out the force on one end of a fulcrum, the less force needs to be applied to achieve a force in the opposite direction. This means is that the mechanical advantage is inversely proportional to the output length and directly proportional to the input length.
A crank is a lever that is able to be rotated 360 degrees about its pivot. While it doesn’t look like a pivot, the mathematics behind it is the same. Wheels and gears do the same thing. Figure 50 shows the mechanical advantage of a crank:
