1. Levers A lever is a rigid bar that pivots (rotates) about a fixed point. Levers are used to change the magnitude, direction, or speed of forces that act on an object. Levers are simple machines used to obtain a Mechanical Advantage.

2. What Is a Lever ? A lever can be a bar or rod that rotates on a pivot, called a fulcrum. When an unbalanced force is applied to the lever, the lever rotates about the fulcrum

3. Parts of a Lever Distance From Fulcrum to The Effort Load or Resistance FULCRUM Force or Effort Distance From Fulcrum to The Resistance

4. Class 1 Lever The Fulcrum lies between the Resistance and the Effort 10 Inches Load or Resistance FULCRUM Force or Effort 10 Inches Note: The movement of the force and the resistance are in opposite directions.

5. Note that in this example the masses are different, but the distances from the fulcrum are equal. The lever rotates about the fulcrum. The unbalanced force that causes the lever to rotate is called a Torque

6. Class 2 Lever Note: The direction of the force, and the movement of the resistance are in the same direction. 10 Inches Load or Resistance FULCRUM Force or Effort 10 Inches The resistance is between the Effort and the Fulcrum

7. Note: In this example the Effort acts further from the Fulcrum then the Resistance. The force (in lbs.) needed to move the resistance is less than the weight of the resistance (in lbs.)

8. Class 3 Lever 10 Inches Load or Resistance FULCRUM Force or Effort 10 Inches The Effort is between the Resistance and the Fulcrum Note: The direction of the force, and the movement of the resistance are in the same direction.

9. Third class levers are used to increase the rate of motion (speed) of an object with respect to the speed of the force acting on the object. In this example the Resistance moves twice as far (fast) as the effort (force) acting on it.

10. Mechanical Advantage

11. Theoretical Mechanical Advantage The ratio between the Output force and the Input force of a lever system. 10 feet1 foot 100 lbs. 1000 lbs. Center of Mass Center of Effort Output Force = 1000 lb.Input Force = 100 lb. Theoretical Mechanical Advantage = 10:1 Force or Effort Load or Resistance 100lb x 10ft. = 1000lb. X 1ft.

12. Calculating Mechanical Advantage Effort x Distance = Resistance x Distance 10 feet1 foot 100 lbs.1000 lbs. Center of Mass Center of Effort Input Force = 100 ft.lbs. Force or Effort Load or Resistance Output Force = 1000 ft. lbs. 100lb x 10ft. = 1000lb. X 1ft.

13. If the Effort x distance from the fulcrum is not equal to the the Resistance x distance from the fulcrum, then; 100 lbs. x 20 ft. = 500 x 15 ft. 20 Feet 15 Feet 100 lbs. 500 lbs. The Lever System is Unbalanced Force or Effort 100 lbs. Load or Resistance 2000 lb.ft. = 7500 lb. ft. A net torque of 5500 ft. lbs is created

14. Example: When the loads are equal but the distances are not, the lever is not balanced. 100 x 10 = 100 x 30 10 Feet 30 Feet 100 lbs.

15. There are many types of levers found around the home Nail Extractor Fulcrum Effort Resistance or Load Class 1 Lever

16. Hammer Effort Resistance or Load Fulcrum Class 3 Lever

17. Salad Server Effort Resistance or Load Fulcrum 2 Class 1 Levers Sharing a Common Fulcrum

18. This backhoe is an example of a multiple lever. It has three different fulcrums.

19. The asterisks show the locations of each fulcrum * * *

20. The Trebuchet A class 1 lever used to maximize the speed of a relatively lightweight projectile (Resistance) by using a massive counterweight (Effort) to create a large unbalanced force