Getting to Know: Lever
What do the following have in common: a seesaw, a wheelbarrow, and a baseball bat? They’re all levers, which is one of the six types of simple machines.
The lever is a simple machine consisting of a plank that rotates at a fixed point called a fulcrum. One of the oldest tools, levers may have been used as far back as prehistoric times. The Greek mathematician Archimedes described how a A seesaw is an example of a lever.
seesaw could be balanced based on the weights of two objects and their distance from the center. Nowadays, levers are used everywhere. In fact, there are several types of levers, and you probably at some time or another have used all of them. What are the basic types of levers?
A basic lever has four components. The first is the
plank, which is a rigid object of some length, like a
piece of wood. The object being moved is called a
load, and the force applied to the simple machine
is called the effort. In the case of tools, effort is
usually applied through a human hand. The last
component needed is something for it to rest on
that will allow the lever to pivot, also called the
fulcrum.
The basic classes of levers have to do with the
location of the effort, load, and fulcrum along the
lever itself. In a first-class lever, like a seesaw, the
fulcrum is in the middle of the lever, the load is on one end, and the effort is applied to the
other. In both the second- and third-class levers, the fulcrum is at one end and the difference
between them is defined by the location of the load and effort. In a second-class lever, the
load is in the middle of the lever and the effort is at the other end, like in a wheelbarrow. In a
third-class lever such as a baseball bat, the load is at the end and the effort is in the middle.
A wheelbarrow uses a second-class lever.
Concept: Lever
Getting to Know
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Misconception 1: Don’t all machines have motors in them?
No, machines are not defined as having motors. A machine is any device that modifies or
transmits an effort force. There are six types of simple machines: the inclined plane, the
lever, the wheel and axle, the pulley, the wedge, and the screw.
How does a lever help to get work
done?
A lever magnifies the effort force so that it takes
less effort to perform work. Just think of how
hard it would be to hit a baseball into left field
with just your hand! Mechanical advantage, the
ratio of the effort force to the total force exerted
on the load by the lever, describes how much a
simple machine changes the effort force. A lever
multiplies the effort force exerted by a person
so that they can do the same amount of work
more easily.
A baseball bat magnifies the effort force.
Misconception 2: I thought a lever reduced the amount of work. Is that right?
A lever doesn’t reduce the amount of work required to move the load. To move a load,
there must be a force greater than the gravity and friction acting on the load. Levers and
other simple machines reduce the amount of effort that must be exerted by a person,
but the same amount of work is required to move a load.
Are levers used in other types of machines?
Two or more simple machines can be used together to build a complex machine. A complex
machine is a system in which parts work together to accomplish a task. In fact, a wheelbarrow
is a complex machine consisting of a lever and another simple machine called a wheel and
axle. Together they are able to not only lift a load, but also to move it around.
In this lesson, you will learn more about the different classes of levers and how they can be used with other simple machines.
Concept: Lever
Getting to Know
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© Discovery Education. All rights reserved.
Discovery Education is a subsidiary
of Discovery Communications, LLC.