Facts At Your Fingertips: Energy and forces – Simple machines
We use simple machines to help us do our work more easily.
There are six kinds of simple machine. They change the direction or size of a force, allowing us to use less effort when moving, separating, or keeping heavy objects in place.
Inclined planes
An inclined plane, or ramp, is a sloping surface. It reduces the force needed to lift an object by increasing the distance it has to travel. A screw is an inclined plane wrapped around a cylinder, which moves in a circle.
Wedges
A wedge is a triangular-shaped machine. It changes a force applied to its blunt end into a force that pushes outward.
Wedges can be used to cut through objects— as with an ax cutting through wood—or to hold objects in place, like a wedge holding open a door.
Wheels
A wheel is a machine attached to a central shaft, or axle. The axle and wheel turn together.
Monster trucks have huge wheels, which allow them to ride over large obstacles, including cars. Each turn of the wheels moves the truck a long distance.
Gears
Gears are wheels with teeth. Connected together, gears transfer a force from one place to another and can change the size of the force.
Here, the larger yellow gear is twice the size of the smaller blue one. So, for every complete turn of the yellow gear, the blue gear turns twice.
Levers
Simple machines called levers make it easier to lift heavy loads. A lever is fixed at one point, called the fulcrum, and rotates around that point. There are three different classes of lever, depending on the position of the fulcrum, the load, and the effort needed to lift the load.
Pulleys
A pulley is a wheel on an axle with a rope running around it.
A single pulley on its own can change the direction of a force.
Two or more pulleys working together reduce the amount of force needed to lift a load by increasing the distance the rope has to travel.