1. Turning forces and Centre of Gravity
Chapter 43

2. The Turning effect of a force
The turning effect of a force can be increased
in 2 ways.
Increasing the size of the force itself.
By increasing the distance of the applied force
to the fulcrum.
The point about which the object turns is referred to as the fulcrum.

3. Moment of a force
The moment of the force or the turning effect of the force.
Moment of a force = (Force) x (perpendicular distance from the force to the fulcrum)

4. A Lever used to turn a tap

5. What is the moment of the force(turning effect) that is being exerted in the following diagram?
Answer:
Moment = Force x distance from fulcrum
40N x 0.2m =8 Nm

6. Levers
A lever is a rigid body which is free to turn about a fixed point called the fulcrum.
Examples of Levers:
A door, wheelbarrow, crowbar, see-saw,

7. Here are 3 examples of lever’s
Here are 3 examples of lever’s. In each case identify which is the effort, load and fulcrum

8. Answer

9. Levers
Levers can be used to exert a large force over a small distance at one end by exerting only a small force over a greater distance at the other

10. The law of the lever
The Law of the lever states that when a lever is balanced , the sum of the clockwise moments are equal to the anti-clockwise moment.

11. Balancing a Meter Stick

12. Is This Meter Stick Balanced?

13. Is this lever balanced?
Left Hand side
Moment = Force x Distance
1N x 40cm
= 40 Ncm
Right Hand Side
= 2N X 25cm
= 50Ncm
Therefore The Lever is not Balanced.
Where must the 2N weight be placed to have a balanced meter stick?

14. What is the value of y?

15. Where must the 32N weight be hung to balance the meter stick?

16. Find the Weight of the stone

17. Question:
Calculate where the 5N weight must be placed so as to have a balanced lever?

18. Left Hand Side
Right hand side
5 x y = 5y
x 12 = 96
Total Y
13 x 7 = 91
6 x 18 = 108
x 46 = 92
Total
=291
5Y =
5Y = 195
Y = 39
Therefore the 5N weight is at the 11 cm mark

19. Center of Gravity.
The center of gravity of an object is the point through which the weight of an object appears to act.

20. To find the center of gravity of a sheet of cardboard:

21. Equilibrium
A body is in stable equilibrium if, when slightly moved or tilted, its center of gravity rises.
A body is in unstable equilibrium if, when slightly moved or tilted, its center of gravity falls.
A body is in neutral equilibrium if, when slightly moved or tilted, its center of gravity neither rises or falls.

22. Types of Equilibrium

23. Equilibrium

24. Equilibrium

25. Objects in stable equilibrium will have a wide base and a low center of gravity.
In designing a bus, for example, a low center
of gravity makes a bus more stable and less
likely to topple over.

26. Unstable equilibrium