The Simple Physics of Seesaws

The Physics of a Seesaw

A seesaw involves some of the most basic aspects of physics. It is essentially a lever: a long, rigid arm that

hinges on a pivot point called a fulcrum. A lever is essentially a mabasic chine that transmits energy in

order to do work. A lever does the work for you, allowing you to lift objects you'd never be able to lift by

yourself.

Understanding Torque

To understand the way a seesaw works, think about pushing a door, which is another kind of lever. If you push near the hinge, it's pretty difficult to open. It's much easier to push on the end of the door opposite the hinge, and it's best to push at right angles to the door. This is a result of the principle of torque, or the force of rotation. Torque is the product of the rotational force exerted at right angles on the lever, times the distance between the point of force and the fulcrum.

On a seesaw, if two children are roughly the same weight and they're each sitting on the opposite ends

equal distance from the center, the whole thing will be balanced because they're exerting equal and

oppositely directed forces. However, if one child is significantly heavier than the other, the heavier one

will have to move closer to the center to achieve this equilibrium. Altering the force's distance from the

fulcrum clearly affects the rotational force exerted on the other side.

Doing Work with Torque

A 50-pound child would probably not be able to lift a 100-pound child on his own, but he can easily do this on the seesaw just by changing his or her position. However, the lighter child will travel a farther distance (up and down) than the heavier child, as the fulcrum of a lever allows us to easily manipulate the relationship between force and distance.

The same principle is at work when you use the claw of a hammer to remove a nail. As you pull the nail
straight out, it is more difficult than resting the hammerhead (the fulcrum) and rolling it with the end of
the handle (the lever arm) to pull out the nail. The arc of your hand will follow a longer distance than if
you just tried to pull it straight out, but you'll be exerting less force to do the same work.

Sources
http://www.discovery.com/tv-shows/mythbusters/about-this-show/physics-of-seesaws/
https://www.youtube.com/watch?v=YlYEi0PgG1g