1 st , 2 nd , & 3 rd class Levers Give me a lever long enough and a fulcrum on which - PowerPoint Presentation

1st, 2nd, & 3rd class LeversGive me a lever long enough and a fulcrum on which to place it, and I shall move the world. -Archimedes Levers: Gaining More Leverage

1st class levers review:Look at the 1st class lever below.Identify the FELLA Think of at least 3 facts related to 1 st class levers to share with the classDiscuss

1st class levers reviewF = fulcrumE = effort L = loadL = leverA = 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 Place the load near the fulcrum and the effort far from the fulcrum for easier lifting.

Let’s look at more 1st Class leversExamples in strength trainingClass 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.

More classes of leversLook at the diagram below.What differences can you see between the different classes of levers?

Classes of LeversLevers can be set up in three basic ways… Class 1 – fulcrum middleClass 2 – load middle Class 3 – e ffort middle Remember: FLE = 123

2nd Class LeversCan 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 trainingClass 2 - Standing heel lift Try a standing heel lift and see your body work as a 2 nd 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 1 st 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 (= an 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 3 rd 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 . [Newton’s Law] 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? 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!

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.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 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?

3rd Class LeversClass 3 - The fulcrum is at one end, the load at the other end and the effort lies between the load and the fulcrumThe third class lever is the strangest ... and the one you use the most! 3 rd class levers do not give any mechanical advantageSo 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 LeversExamples:

3rd Class Lever Examples

They help us do work…

3rd Class Lever ExamplesThey help us in sports!

Many sports are played with 3rd Class Levers!!!

3rd Class Lever ExamplesCan you identify my FELLA?

Examples in strength trainingClass 3 - Seated biceps curl Try a seated biceps curl and see your body work as a3rd class lever! Effort is applied between the wrist and the elbow.

More Examples of 3rd Class LeversDouble 3rd class levers

Levers ReviewCan you identify which class lever I am?

Let’s reinforce…Read pages 12-13 on levers in your “Levers & Pulleys” bookBe 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