1. Levers

2. effort
resistance
A lever consists of a rod or bar that rests and turns on a support called a fulcrum.

3. A force of effort is applied at one end of the rod to lift a load placed at the other end. A lever can help lift a weight with less effort.
effort
resistance
fulcrum

4. Prying something loose with a crowbar is using a lever
Prying something loose with a crowbar is using a lever. Some machines, such as a catapult, use a lever to hurl objects.

5. Here is a catapult you could make.

6. Three Classes of Levers
First Class Lever
The fulcrum is between the effort force and the resistance force.
effort
resistance
fulcrum

7. Three Classes of Levers
Second Class Lever
The resistance is between the effort and the fulcrum.

8. Three Classes of Levers
Third Class of Lever
The effort is between the fulcrum and the resistance.

9. First Class Lever
Second Class Lever
Third Class Lever

11. Levers in the Body How bones and muscles work together!

12. Work is the ability to apply a force that moves a body in the direction of that force.

13. Levers makes work easier by changing:
the amount of force.
the distance over which the force is exerted.
the direction of the force.

14. 1st Class Lever
An example of a first-class lever is the joint between the skull and the atlas vertebrae of the spine: the spine is the fulcrum across which muscles lift the head.

15. 2nd Class Lever
An example in the human body of a second-class lever is the Achilles tendon, pushing or pulling across the heel of the foot.

16. 3rd Class Lever
An example of a third-class lever in the human body is the elbow joint: when lifting a book, the elbow joint is the fulcrum across which the biceps muscle performs the work.

18. What types of levers are all of these?
Third Class Levers

19. Mechanical advantage is the number of times a lever increases a force exerted on it.

20. Let’s Practice Name the type of Lever Point to the Fulcrum
Point to the Effort
Point to the Load

21. First Class Lever
Effort
Load
Fulcrum

22. Third Class Lever
Effort
Load
Fulcrum

23. Second Class Lever
Load
Effort
Fulcrum

24. Third Class Lever
Effort
Load
Fulcrum

25. First Class Lever
Load
Effort
Fulcrum

26. Third Class Lever
Fulcrum
Effort
Load

27. The End