Getting to Know: Inclined Plane
It may not seem like it, but every day you are doing work just by moving around. Because your body has mass, work is done every time your muscles apply forces to make your bones move. If you move around a lot in a day or have to run really fast, it’s no wonder that you get tired because of all the work you’ve done. However, simple machines are all around us to make work easier.
You may have been to a school, mall, or stadium where you can enter either by the stairs or by a ramp. Some people prefer to use the ramp because lots of stairs can make you tired. Others need the ramp because they are in a wheelchair. Without realizing it, people who use the ramp are using a simple machine called an inclined plane.
A ramp is a simple machine called an
inclined plane.
An inclined plane is a flat surface that connects an object at one height to an object at another
height. It is a slanted surface or slope. Although we usually think that machines have moving
parts, an inclined plane doesn’t move at all.
How does an inclined plane make work easier?
Remember that a force is a push or a pull and the force of gravity is constantly pulling down
on everything. To lift an object, including your leg, you must apply a force that is greater than
the force of gravity to lift it. This force is the input force. Because you are applying a force over
a distance, you are doing work.
Now when you climb stairs, you must lift your foot up and move it forward a certain distance.
The input force required to do this comes completely from your body. With an inclined plane,
the ramp itself provides some of the vertical input force by redirecting your forward motion
upward. This means that the vertical input force required is less, so it doesn’t feel like such
a climb.
Although the amount the inclined plane contributes is small, it adds up. In fact, the longer the
distance, the less input force required to lift the object.
Concept: Inclined Plane
Getting to Know
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Misconception 1: I thought all machines had motors.
No, machines are devices that modify or transmit a force. Although a motor does
this too, many other machines accomplish this without a motor. Examples of simple
machines that do this are the inclined plane, the lever, the wheel and axle, the pulley,
the wedge, and the screw.
How much does an inclined plane help in getting work done?
The mechanical advantage of an inclined plane is related to its length and height. The
mechanical advantage of an inclined plane is the distance over which a force is applied, that
is, the length of the ramp multiplied by the height that the object
is being lifted. So the longer the ramp, the greater the mechanical
advantage and the less input force that needs to be exerted.
Are inclined planes used in other types of
machines?
When two or more simple machines are combined, they are called
compound or complex machines. However, there is a simple machine
that contains an inclined plane: the screw. A screw is simply an
inclined plane wrapped around a cylinder. Screws are used to hold
things together, but a larger example of a screw is a spiral staircase
or a ramp in a multistory parking garage. Another simple machine
that uses inclined planes is a wedge, which consists of two inclined
planes on opposite sides that is used to push objects apart. A good
example of a wedge is an axe used to chop wood.
A screw is an inclined
plane wrapped around a
cylinder.
Simple machines such as inclined planes are all around us. As you
explore this concept, you will learn a lot more about inclined
planes and how they are used in many types of machines.
Misconception 2: Do inclined planes make less work? Is that what all machines do?
Machines do not reduce the amount of work required. What they do is contribute to the
input force or change its direction so that the input force required by people is reduced.
Concept: Inclined Plane
Getting to Know
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© Discovery Education. All rights reserved.
Discovery Education is a subsidiary
of Discovery Communications, LLC.