POWERFUL LEVERS

One of the simplest and oldest gadgets in the world is the lever. Any rod or stick can act as a lever, helping to move heavy objects or prise things apart. Leavers are also used for lifting, cutting, and squashing. The action of a lever can make a push more forceful, or make it a smaller push. It can make a push more forceful, or make it a smaller push. It can also change the direction of a push. The difference between the sizes of the push you make on a lever (the effort) and the push the lever itself makes (the load) is called mechanical advantage.

A lever on a central pivot can also be used as a balance. The lever balances if the effect of the force (push) on one side of the pivot is the same as the effect of the force on the other. A seesaw is one sort of balancing lever. It is a plank balanced on a central post or pivot. A big person can balance someone small and light if they sit nearer to the central pivot of the seesaw.

How a lever works
A lever tilts on a pivot, which is nearer to the end of the lever with the load on it. The effort, or force, is the push you make on the long end of the lever to lift the weight of the load.

LEVERS AND LIFTING

Ruler, book, pivot (box).

STEP 1
A ruler can be used as a lever to lift a book. With the pivot near the book, only a small effort is needed to lift the book up. The lever makes the push greater.

STEP 2
When the pivot is moved to the middle of the lever, the effort needed to lift the book up is equal to the book’s weight. The effort and the load are the same.

STEP 3
When the pivot is near where you are pressing, more effort is needed to lift the book is now larger than the book’s weight.

BALANCING A SEESAW

Pivot, plank of wood (seesaw).

STEP 1
Ask a friend of equal weight to sit on one side of the seesaw, while you sit on the other side. If you sit the same distance from the pivot, you make the seesaw balance.

STEP 2
Ask another friend to join you on the seesaw. By adding another person, that side of the seesaw will overbalance. The pair’s greater weight will easily lift the lighter person.

STEP 3
Get the pair to move nearer to the pivot of the seesaw. Their weight can be balanced by the lighter person moving farther away from the pivot. The seesaw will be equally balanced.