Lab - Levers
Name_________________________________
Fulcrum: The balancing point on a lever.
Effort Force: The point at which you apply force to a lever.
Load Force: The weight of the object you are trying to move.
1st Class Lever: Effort and load forces are on opposite sides of the fulcrum.
2nd Class Lever: Load is between the fulcrum and the effort force.
3rd Class Lever: Effort force is between the fulcrum and the load.
Actual Mechanical Advantage = Load Force / Effort Force
Ideal Mechanical Advantage = Effort Distance / Load Distance
Part I: First Class Levers
Set up a first class lever according to each trial in the data table and record the data for
the forces involved. All distances are measured from the fulcrum.
Effort
Load
Force
Force
Ideal
Effort
Load
Distance
Distance Mechanichal Mechanical
Trial
Force (N) Force (N)
(cm)
(cm)
Advantage
Advantage
1
40
40
2
40
20
3
40
10
4
30
40
Part II: Second Class Levers
Set up a second class lever according to each trial in the data table and record the data for
the forces involved. Distances are measured from the fulcrum.
Effort
Load
Force
Force
Ideal
Effort
Load
Distance
Distance Mechanichal Mechanical
Trial
Force (N) Force (N)
(cm)
(cm)
Advantage
Advantage
1
40
30
2
40
20
3
40
10
Part III: Third Class Levers
Set up a third class lever according to each trial in the data table and record the data for
the forces involved. Distances are measured from the fulcrum.
Effort
Load
Force
Force
Ideal
Effort
Load
Distance
Distance Mechanichal Mechanical
Trial
Force (N) Force (N)
(cm)
(cm)
Advantage
Advantage
1
30
40
2
20
40
3
10
40
Analysis Questions
1. In a first class lever, what happens to the effort force as the fulcrum gets closer to the
load? What happens to the mechanical advantage?
2. When the fulcrum is very close to the load and the effort force is far from the fulcrum,
how does the distance your hand moves compare to the distance the load moves?
3. When might you want to use a lever that is set up as described in question 2?
4. With a second class lever, where would you place a load so that the least amount of
force is required to lift the load? Explain.
5. Would a second class lever be a good machine for lifting a heavy load? Give an
example of a machine that contains a second class lever.
6. In a third class lever, what happens to mechanical advantage as the effort force gets
closer to the fulcrum?
7. Can a third class lever have a mechanical advantage greater than one? Give an
example of a machine containing a third class lever.