Chapter 8 Machines
229
The Lever
You have probably played or seen a game of baseball. See Figure 8-3.
A baseball bat is a lever. A lever has a fulcrum, effort, and resistance. The r
fulcrum is the point where the bat is held. The batter’s muscles supply
the effort, and the resistance is the ball. See Figure 8-4.
To understand the principle of the lever, look at the boy in Figure 8-5.
He is using a branch to move a heavy rock. The branch is the lever. The mass
of the larger rock is the resistance (R). The boy’s muscle power pushing
down on the lever provides the effort (E). The smaller rock on which
the lever is pivoting is the fulcrum (F). These three elements—resistance,
effort, and fulcrum—are always present in a lever. However, they can be
arranged in different ways to create three different classes of levers.
In a Class 1 lever, the fulcrum is placed between the effort and the
resistance, as shown in Figure 8-6. Some applications of Class 1 levers are
illus trated i n Figure 8-7.
In Class 2 levers, the resistance is placed between the effort and the
fulcrum, as shown in Figure 8-8. Some applications of Class 2 levers are
illustrated in Figure 8-9.
F
R
E
gure 8-4. The baseball bat is an example
of a lever: F–Fulcrum; R–Resistance; E–Effort.
gure 8-3. Baseball players use a bat as a
lever to strike the baseball with greater speed.
R
F
E
gure 8-5.
heavy load.