1 st, 2 nd, & 3 rd class Levers Levers: Gaining More
Leverage
Slide 2
1 st class levers review: Look at the 1 st class lever below.
Identify the FELLA Think of at least 3 facts related to 1 st class
levers to share with the class Discuss
Slide 3
1 st class levers review F = fulcrum E = effort L = load L =
lever A = arm 1 st 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
Slide 4
Lets 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 1 st class
lever.
Slide 5
More classes of levers Look at the diagram below. What
differences can you see between the different classes of
levers?
Slide 6
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
Slide 7
2 nd Class Levers Can you identify my FELLA?
Slide 8
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
Slide 9
Other examples of 2 nd class levers Examples in strength
training Class 2 - Standing heel lift Try a standing heel lift and
see your body work as a 2 nd class lever!
Slide 10
Other examples of 2 nd 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 1 st
class levers
Slide 11
Lets 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 nutthe load is the resistance of the nut pushing back
(= and opposite force anyone?)
Slide 12
But Miss Lamb, Im still confused??? I can easily find the
effort and fulcrum. Why are the arrows for the load pointing away
from the hot dog? [double 3 rd class lever] Effort is applied to
the tongs causing a force against the hot dogthe hot dog resists by
pushing back with an opposing = force. The load is the resistance
pushed back by the hot dog.
Slide 13
Lets try to identify FELLA
Slide 14
Slide 15
Yes, paper can push against the blades!
Slide 16
Fireplace bellow anyone?
Slide 17
Slide 18
How will the 2 nd 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?
Slide 19
Lets try it Take a look at the 2 nd class lever. What is
happening? The load will always pull down, but the effort will
always have to pull up to counteract the load. Note: Now that the
scale is pulling up, you DO NOT need to add.5N
Slide 20
Lets discover more for ourselves Work with your teacher to set
up a 2 nd 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!
Slide 21
Stop here for today!
Slide 22
Lets review before we get started! 1. Use the machines graphic
organizer to draw an illustration of a 1 st and 2 nd class lever.
2. Read page 10-11 in your Levers & Pulleys textbook. 3. Answer
the following questions: 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 2 nd class levers.
Slide 23
Experiment & Discover Set up your 2 nd 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?
Slide 24
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 2 nd and 3 rd 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?
Slide 25
3 rd 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 3 rd 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.
Slide 26
3 rd Class Levers Examples:
Slide 27
3 rd Class Lever Examples
Slide 28
They help us do work
Slide 29
3 rd Class Lever Examples They help us in sports!
Slide 30
Many sports are played with 3 rd Class Levers!!!
Slide 31
3 rd Class Lever Examples Can you identify my FELLA?
Slide 32
Examples in strength training Class 3 - Seated biceps curl Try
a seated biceps curl and see your body work as a3rd class
lever!
Slide 33
More Examples of 3 rd Class Levers Double 3 rd class
levers
Slide 34
Levers Review Can you identify which class lever I am?
Slide 35
Lets 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 3 rd class lever picture Look closer
at everyday objects & determine their class
