1. Levers & Moments

2. Levers
Forces can move objects by turning them around a pivot or fulcrum. A long bar that pivots is a lever. When you push down on one side, you are applying force. The object on the other end (the load) moves up. Using a lever magnifies the force and makes objects easier to move.
Load moves up when force applied
Force
Load
Pivot/Fulcrum

3. Types of Levers – First Order
In this type of lever the pivot (or fulcrum) is between the effort and the load as in the simple crowbar.

4. Types of Levers – Second Order
In this type of lever the load is between the effort and the pivot (or fulcrum) as in the wheelbarrow.

5. Types of Levers – Third Order
In this type of lever effort is between the load and the pivot (or fulcrum) as in the pair of tweezers.

6. Task: Jenny is using a lever to lift this large box.
1. Label the diagram of this with the following key words:
Load
Pivot
Force
2. Do you think it would be easier to lift the box with a shorter lever? Explain your answer.

7. As Jenny applies force to the lever, she exerts effort at one end.
Task:
As Jenny applies force to the lever, she exerts effort at one end.
The effort (force downwards) causes the load on the other end of the lever to move upwards.
Effort
Load
Pivot/Fulcrum

8. moment = force (N) x perpendicular distance from pivot (cm or m)
Moments
The moment or “turning effect“ can be calculated using the following equation:
moment = force (N) x perpendicular distance from pivot (cm or m)
moment f x d
Moments are measured in Newton centimetres (N cm) or Newton metres (N m).

9. Calculate the moment:
10 cm
50 N cm
5 N
pivot

10. Calculate the moment
5 cm
25 N cm
5 N
pivot

11. Calculate the moment:
10 cm
100 N cm
10 N
pivot

12. Calculate the force:
2 m
Moment
= 500 N m
250 N
Force

13. Balanced Moments: 10 m 10 m 10 N 10 N pivot Left Moment Right Moment
100 N m
100 N m
10 N
10 N
pivot

14. Balanced Moments: 10 m 7 m pivot 10 N 10 N Left Moment Right Moment
100 N m
70 N m
pivot
10 N
10 N

15. Balanced Moments: 20 N 10 N pivot 10m 10 m Left Moment Right Moment
100Nm
200Nm
20 N
10 N
pivot

16. Balanced Moments 10 m 5 m 10 m 20 N 10 N pivot Left Moment Right
100Nm
100Nm
20 N
10 N
pivot

17. Principle of moments
For an object to be in equilibrium (balanced), the following two conditions must be true:
The total upward force is equal to the total downward force.
The sum of the anticlockwise moments is equal to the sum of the clockwise moments

18. Calculate the load on each side and say if the level is balanced, will move clockwise, or will move anticlockwise.
Balanced
Will move anticlockwise
Will move clockwise
Will move anticlockwise

19. Question
Why is it easier to open a tin of paint with a screw driver than with your bare hands?

20. Question
Why is it easier to open a tin of paint with a screw driver than with your bare hands?
The screwdriver acts as a first order lever. The pivot (fulcrum) is at the point where the effort is applied on the lid. By using a screwdriver, you increase the distance at which the effort is applied. This increases the moment, making it easier to open the lid.