The Wheel and Axle
A wheel and axle is really
two machines in one because you can use each part in different ways. The first
way is to roll something along. Wheels help you move an object across the ground
because they cut down on the amount of friction between what you're trying to
move and the surface you're pulling it against. (The axle is the object that
attaches the wheel to the object it's moving.) Since only the very bottom of the
wheel touches the ground, there is less surface area to rub — and less friction.
Imagine pulling a little red wagon without any wheels! Generally speaking, the
bigger the wheel, the easier it is to make something roll.
The
second way of using a wheel is like a lever in the round. A door knob or a
faucet on a sink are really round levers, and the "fulcrum" is in the middle
where the axle turns. Imagine if a door knob was replaced with a little rod. It
would be much harder to open the door! Once again, there's a trade-off: The
larger the diameter of the wheel, the less effort you need to turn it, but you
have to move the wheel a greater distance to get the same work done.
A wheel and axle has a larger wheel (or wheels) connected by a
smaller cylinder (axle) and is fastened to the wheel so that they turn together.
When the axle is turned, the wheel moves a greater distance than the axle, but
less force is needed to move it. The axle moves a shorter distance, but it takes
greater force to move it.
Examples: car wheel, toy car.
A wheel and axle is really
two machines in one because you can use each part in different ways. The first
way is to roll something along. Wheels help you move an object across the ground
because they cut down on the amount of friction between what you're trying to
move and the surface you're pulling it against. (The axle is the object that
attaches the wheel to the object it's moving.) Since only the very bottom of the
wheel touches the ground, there is less surface area to rub — and less friction.
Imagine pulling a little red wagon without any wheels! Generally speaking, the
bigger the wheel, the easier it is to make something roll.
The
second way of using a wheel is like a lever in the round. A door knob or a
faucet on a sink are really round levers, and the "fulcrum" is in the middle
where the axle turns. Imagine if a door knob was replaced with a little rod. It
would be much harder to open the door! Once again, there's a trade-off: The
larger the diameter of the wheel, the less effort you need to turn it, but you
have to move the wheel a greater distance to get the same work done.
A wheel and axle has a larger wheel (or wheels) connected by a
smaller cylinder (axle) and is fastened to the wheel so that they turn together.
When the axle is turned, the wheel moves a greater distance than the axle, but
less force is needed to move it. The axle moves a shorter distance, but it takes
greater force to move it.
Examples: car wheel, toy car.