Levers
Simple machines are simple tools used to make work easier. Compound machines have two or more simple machines working together to make work easier. | |
In science, work is defined as a force acting on an object to move it across a distance. Pushing, pulling, and lifting are common forms of work. Furniture movers do work when they move boxes. Gardeners do work when they pull weeds. Children do work when they go up and down on a see-saw. Machines make their work easier. The furniture movers use a ramp to slide boxes into a truck. The gardeners use a hand shovel to help break through the weeds. The children use a see-saw to go up and down. The ramp, the shovel, and the see-saw are simple machines. |
Simply put, levers are machines used to
increase force. We call them "simple machines" because they have only
two parts — the handle and the fulcrum. The handle or bar of the lever is
called the "arm" — it's
the part that you push or pull on. The "fulcrum" is the point on which
the lever turns or balances. In the case of a fork, the fulcrum is the fingers
of your hand. Scissors are really two levers put together. The handle on the
toilet flusher is commonly called a fixed lever. Take a quick look around you
and see how many levers you can find.
Try pulling a really stubborn weed out of the ground. You know, a deep, persistent weed that seems to have taken over your flowerbed. Using just your bare hands, it might be difficult or even painful. With a tool, like a hand shovel, however, you should win the battle. Any tool that pries something loose is a lever. A lever is an arm that "pivots" (or turns) against a "fulcrum" (or point). Think of the claw end of a hammer that you use to pry nails loose. It's a lever. It's a curved arm that rests against a point on a surface. As you rotate the curved arm, it pries the nail loose from the surface. And that's hard work! |
These are all different kind of levers: