Transcript Classes of Levers

Levers: Gaining More Leverage
1st, 2nd, & 3rd class Levers
1st class levers review:
 Look at the 1st class lever below.
 Identify the FELLA
 Think of at least 3 facts related to 1st class levers to share
with the class
 Discuss
1st
class levers review
 F = fulcrum
 E = effort
 L = load
 L = lever
 A = arm
1st Class Facts:
The fulcrum is
always in the middle
Effort applied down,
pulls the load up
Levers provide a
mechanical advantage
making work easier
The closer the load is
to the fulcrum, the less
effort it takes to lift the
load
The further the
effort is from the
fulcrum, the easier it is
to lift the load
Let’s look at more 1st Class levers
Examples in strength training
 Class 1 - Seated dumbbell triceps extension
 Try it!
 Place a heavy book in your arm and see your body work as a 1st
class lever.
More classes of levers
 Look at the diagram below.
 What differences can you see between the different classes of
levers?
Classes of Levers
 Levers can be set up in three basic ways…
Class 1 – fulcrum middle
Class 2 – load middle
Class 3 – effort middle
Remember: FLE = 123
2nd Class Levers
 Can you identify my FELLA?
How did you do?
Class 2 - The fulcrum is at one end, the effort at the other
end and the load lies between the effort and the fulcrum
Other examples of 2nd class levers…
Examples in strength training
 Class 2 - Standing heel lift
 Try a standing heel lift and see your body work as a 2nd class
lever!
Other examples of 2nd class levers…
Class 2 - Standing heel lift
 Where is the load?
 Would you be able to locate the load in this
illustration if it were not labeled?
 Why is the load sometimes difficult to
identify in a class 2 lever?
 RESISTANCE CAN BE CONSIDERED LOAD!!!
 Remember the example of the oar from our 1st class levers…
Let’s explore this further…
 Look at the example of the nutcracker
 The weight of the nut IS NOT the load. (The nutcracker is not
designed to move the nut around. It is designed to crush the nut)
 When you squeeze the ends of the lever, the jaws of the
nutcracker push on the nut…the load is the resistance of the
nut pushing back (= and opposite force anyone?)
But Miss Lamb, I’m still confused???
 I can easily find the effort and fulcrum.
 Why are the arrows for the load pointing away from the hot dog?
[double 3rd class lever]
 Effort is applied to the tongs causing a force against the hot
dog…the hot dog resists by pushing back with an opposing =
force.
 The load is the resistance pushed back by the hot dog.
Let’s try to identify FELLA…
 Yes, paper can push against the blades!
Fireplace bellow anyone?
How will the 2nd class lever work?
 If the load and effort are found on the same side of the
fulcrum, what does this mean will happen when we pull
down?
Let’s try it…
 Take a look at the 2nd class lever.
 What is happening?
Note: Now that the
scale is pulling up,
you DO NOT need
to add .5N
 The load will always pull down, but the effort will always
have to pull up to counteract the load.
Let’s discover more for ourselves…
 Work with your teacher to set up a 2nd class lever system.
 In this case, you will be measuring load (not resistance) and
the effort that it takes to lift the load
 Experiment.You will have to lift up with your spring scale,
what will happen to the load?
 Will you have to add .5N to your calculations?
 What happens when you move the load closer to the
fulcrum?
Complete the response sheet for more leverage!
Stop here for today!
Let’s review before we get started!
Use the “machines” graphic organizer to draw an
illustration of a 1st and 2nd class lever.
2. Read page 10-11 in your “Levers & Pulleys” textbook.
3. Answer the following questions:
1.



What is the mechanical advantage of a class 2 lever?
What is the load in the bellows?
How is the bellows like the nutcracker and garlic press?
Now we are going to explore the advantage rule for 2nd class
levers.
Experiment & Discover…

Set up your 2nd class lever. Set up your load from
your assigned distance from the fulcrum.

Record your findings on the diagram in your
packet.

Travel to the other desks in your row. Apply effort
and record your findings on the diagram in your
packet. When you are finished, return to your seat.

What do you find?
How are these classes different?
 Look at the position of the fulcrum in these pictures.
 What is different about the positions of the load and effort in a 2nd
and 3rd class lever?
 If the load and effort are found on the same side of the fulcrum,
what does this mean will happen when we pull down?
3rd Class Levers
 Class 3 - The fulcrum is at one end, the load at the other
end and the effort lies between the load and the fulcrum
 The third class lever is the strangest ... and the one you use
the most!
 Some 3rd class levers do not give any mechanical advantage
 So why use them?
The answer lies in the fact that the load moves in the same
direction as the force you apply, which is convenient.
3rd Class Levers
 Examples:
3rd Class Lever Examples
They help us do work…
3rd Class Lever Examples
 They help us in sports!
Many sports are played with 3rd Class
Levers!!!
3rd Class Lever Examples
 Can you identify my FELLA?
Examples in strength training
 Class 3 - Seated biceps curl
 Try a seated biceps curl and see your body work as a3rd class
lever!
More Examples of 3rd Class Levers
 Double 3rd class levers
Levers Review
 Can you identify which class lever I am?
Let’s reinforce…
 Read pages 12-13 on levers in your “Levers & Pulleys” book
 Be sure you can answer the following question:
*What is the mechanical advantage of a class 3 lever?
 Complete your graphic organizer by drawing a 3rd class lever
picture
 Look closer at everyday objects & determine their class