Name:
Levers
Levers were probably one of the very first machines. There are three parts to every lever.
One part is the object of weight being moved. It is called the “resistance force.” A push
or pull is needed to move the resistance. This pull or pull is called the “effort force.”
The third part of the lever is called the “fulcrum.” It is the point on the lever where
direction and movement changes.
DIRECTIONS: Label the parts of each lever shown. Each lever will have a fulcrum, a
resistance force, and an effort force.
A. Pliers
B. Hammer pulling
nail from a board
C. Hammer nailing
D. Nutcracker
E. Door handle
F. Prying off
Paint can top
log
There are three classes or kinds of levers. They are called First-class, second class, or
third class levers. What makes one class of levers different from another is where the
force, resistance, and fulcrum are located. Here are some examples:
First-class levers: In this case the fulcrum is located between the force and resistance. A
see-saw is a good example of a first-class lever.
Second-class lever: A second-class lever is set-up so that the resistance is between the
force and fulcrum. A wheelbarrow is a second-class lever.
Third-class lever: In the case of the third-class lever, the force is between the resistance
and the fulcrum. A fishing pole is a good example.
Name:
DIRECTIONS: Identify the levers above as first-class, second-class, or third-class
levers.
A: _________________
B: ____________________
C: ___________________
D: _________________
E: ____________________
F: ___________________
The ideal mechanical advantage (IMA) of a lever is the ideal number of times the effort
force is multiplied. It is determined by dividing the length of the effort arm by the length
of the resistance arm. The (actual) mechanical advantage (MA) is the actual number of
times the effort force is multiplied. It is determined by dividing the resistance force by
the effort force.
IMA = de/dr
MA = Fr/Fe
DIRECTIONS: Solve the following problems. Show all work.
1.) What is the ideal mechanical advantage of a lever with a resistance arm of 1.5 m
and an effort arm of 3 meters?
2.) A lever has an effort arm of 1 meter. The resistance arm is 0.5 meters. What is
the ideal mechanical advantage?
3.) What is the ideal mechanical advantage of a lever where a 8 N force located 4
meters from the fulcrum lifts a 13 N force located 2.1 meters from the fulcrum?
4.) In the above problem, what is the actual mechanical advantage of the lever?
5.) In the above problem, what is the efficiency of the lever?