Three Types of Levers? Let’s see!

The three parts of a lever, fulcrum, resistancearm and effortarm, work together to make it possible to lift a weight using less force. The placement of the fulcrum, resistance and effort on the lever determine what type it is. There are 3 types of levers. They are classified as 1st class, 2nd class, and 3rd class. They can be diagramed as follows:

R E
F / R E
F / E R
F
1st class / 2nd class / 3rd class

Think of some examples of the above levers. Think of any kind of tool or object that you might use to move something else. Can you come up with at least one example for each class of lever? List them in the analysis questions section.

Now let's look at a pry bar. It is a form of a lever. Use the pictures and see how it can be used as three different forms of levers. Each form of a lever has a different distance between the effort arm and the fulcrum.
What class of lever is a pry bar?
....It depends on how it is being used!
Think about each crowbar picture below and circle the type of lever demonstrated:

A

Lifting a nail
First Class?
Second Class?
Third Class? / B

Lifting a nail
First Class?
Second Class?
Third Class? / C

Pounding a nail
First Class?
Second Class?
Third Class?

Now let's apply your knowledge about levers to determine the mechanical advantage of a lever. Mechanical advantage refers to how much the lever seems to increase your effort. The formula for mechanical advantage is as follows:

  1. If you place the effort two meters away from the fulcrum and the resistance two meters away from the fulcrum, what is the mechanical advantage?
  1. If you place the effort two meters away from the fulcrum and the resistance one meter away from the fulcrum, what is the mechanical advantage?
  1. If you place the effort one meter away from the fulcrum and the resistance 10 meters away from the fulcrum, what is the mechanical advantage?
  1. (Toughie) You are hiking in the woods with a friend. A 500 lb boulder falls on him. Knowing that the car keys are in his pocket, you decide to find a lever and pry the boulder off. If you use a 6 foot long lever with 1 foot under the rock and 5 feet from the fulcrum to your hands, how much pressure must you apply to lift the rock up?

5. How does using a lever make lifting an object easier?

a. it reduces the weight of the object
b. it reduces the work
c. it trades force for distance
d. it requires more energy but less work
e. it doesn't make it easier

6. What type of lever is illustrated by the following arrangement?

R E

______

F

a. 1st class lever b. 2nd class lever c. 3rd class lever d. 4th class lever e. 5th class lever

Analysis Questions:
1. Diagram the lever of a seesaw. Label the fulcrum, resistance, and the effort:

2. What does a lever "trade" for force?

3. Name three commonly used levers. 1st class: 2nd class: 3rd class:

111 2 2 2 3 3 3