1. Technology Exploration
ATE 910
Grade 9
Module: #2 Levers (2 – weeks)
Eng. Rose Hasan

2. Module Objectives Identify levers.
Identify levers.
Calculate the mechanical advantage of a lever.
Calculate forces and lengths related to levers.
Distinguish and explain the difference between the three classes of levers.
Give real life examples of the different types of levers.
Eng. Rose Hasan

3. Module Contents Introduction to Levers Mechanical Advantage of Levers
Classes of Levers
Activities
Practical Tasks
Levers Worksheet
Additional Resources
Eng. Rose Hasan

4. Introduction to Levers
Lever is one of the most commonly used simple machines.
A lever is a rigid bar that is used to transfer force. With a pivot or sometimes called fulcrum.
Lever can be used to change force that is applied (effort) by changing the position of the pivot along the lever .
EFFORT, PIVOT (Fulcrum) and LOAD are the three features that are common in every lever.
Eng. Rose Hasan

5. Introduction to Levers
Pivot is the point on which the lever balances (or pivots).
Load is the weight or resistance that needs to be overcome.
Effort is the force you apply to the lever.
Eng. Rose Hasan

6. Mechanical Advantage of Levers
The mechanical advantage of a machine is the ratio of the output force produced by a machine to the applied input force.
In a lever, the ideal mechanical advantage (MAi) of a lever is the ratio of the length of the effort arm (LE) to the length of the load arm (LL).
Eng. Rose Hasan

7. Mechanical advantage of a Lever
Eng. Rose Hasan

8. Mechanical Advantage of a Lever
The amount of effort needed to lift a given load with any lever can be calculated using this formula:
FE x LE = FL x LL
FE: Effort force
LE: Effort arm length
FL: Load force
LL: Load arm length
Eng. Rose Hasan

9. Examples: Calculate the following:
The effort needed to balance the 400 N load given that the load arm length is 0.4 m and the effort arm length is 2 m.
 The ideal mechanical advantage (MAi)
Eng. Rose Hasan

10. Example: Cont. … FE x LE = FL x LL
If the effort arm length is 5 times the load arm length, then the effort force required is 1/5 the load force; i.e. to decrease the effort force, increase the effort arm length.
Eng. Rose Hasan

11. Classes of Levers There are three classes of levers: First class
Second class
Third class
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12. First Class of Levers:
Have the fulcrum (pivot) positioned between the effort and the load
A clear example of the first class levers is a seesaw.
Eng. Rose Hasan

13. Can you think of other examples?
First Class of Levers
Can you think of other examples?
Eng. Rose Hasan

14. Second Class Levers
The load is positioned between the fulcrum (pivot) and effort
A typical example of second class levers is the nut cracker.
Eng. Rose Hasan

15. Third Class Levers
The effort positioned in the middle between the load and pivot.
A typical example of third class levers is tweezers.
In third class levers the effort force is more than the load force, but the effort traveled-distance is less.
Eng. Rose Hasan

16. Homework
Search the internet for different classes of levers with their pictures.
Eng. Rose Hasan

17. Future Plan Be prepared to a Quiz next Class in module #2.
Next Class: Start with Module #3 :
Eng. Rose Hasan