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 • 1stClass 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 • F = fulcrum • E = effort • L = load • L = lever • A = arm
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.
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? • 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
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!
Let’s review before we get started! • Use the “machines” graphic organizer to draw an illustration of a 1st and 2nd class lever. • Read page 10-11 in your “Levers & Pulleys” textbook. • 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 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 in sports!
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