1. 3) Calculate the spanner’s turning effect in newton metres. (2 marks)
April 16, 2017
1)The turning effect of a force is called the …….. …. of the force ( 1 mark)
2) Give two ways in which you can increase the spanner’s turning effect. ( 2 marks)
3) Calculate the spanner’s turning effect in newton metres. (2 marks)

2. use a longer spanner (1 mark) use a greater force / pull (1 mark)
April 16, 2017
1)The turning effect of a force is called the ..momentun …. of the force ( 1 mark)
2) Give two ways in which you can increase the spanner’s turning effect. ( 2 marks)
use a longer spanner (1 mark)
use a greater force / pull (1 mark)

3. 3) Calculate the spanner’s turning effect in newton metres. (2 marks)
April 16, 2017
3) Calculate the spanner’s turning effect in newton metres. (2 marks)
Moment = 20 N x 0.20m (1 mark)
Moment = 4 Nm (1mark)

4. Centre of Mass and stability
April 16, 2017
Centre of Mass and stability
L.O.:
Find out the centre of mass of an object
Explain how the stability on an object may be increased.

5. Homework: any pending questions from workbook pages 104-106
April 16, 2017
Homework: any pending questions from workbook pages

6. CENTRE OF MASS
April 16, 2017
The centre of mass of an object is the point where its mass may be thought to be concentrated.

7. How to find the centre of mass.
April 16, 2017
How to find the centre of mass.
For symmetrical objects, its centre of mass is along the axis of symmetry. If the object has more than one axis of symmetry, its centre of mass is where the axes of symmetry meet.

8. How to find the centre of mass.
April 16, 2017
How to find the centre of mass.
b)When a suspended object is in equilibrium, its centre of mass is directly beneath the point of suspension.
Insert plumbline picuture

9. Tasks: 1) workbook page 104, Q3 2) workbook page 105, Q4-6
April 16, 2017
Tasks:
1) workbook page 104, Q3
2) workbook page 105, Q4-6

10. April 16, 2017
Q6a) Hang the plumb line from the same point as the piece of card. Draw a pencil line on the card along the plumb line Hang the card in a different position and do the same thing again. Where the two lines cross is the centre of mass.

11. April 16, 2017
Q6b)
Repeat the same steps for several pivot points to get multiple lines that will all cross at the centre of mass.

12. Calculate the moment of the girl (2 marks) 360 (Nm)
April 16, 2017
Calculate the moment of the girl (2 marks)
360 (Nm)
What must her father do to increase his moment? (1 mark)

13. move to(wards) the left / to(wards) the / his end 1
April 16, 2017
move to(wards) the left / to(wards) the / his end 1
or move away from the centre / pivot / axis (of rotation) or move away from the girl / the child / his daught

14. April 16, 2017
Stability
L.O.:
Explain how the stability on an object may be increased.

15. What factors affect the stability of an object?
April 16, 2017
What factors affect the stability of an object?

16. April 16, 2017
Stability applet

17. Stability
April 16, 2017
stable
falls over
An object will tend to topple over if the line of actions of its weight is outside its base.

18. April 16, 2017
Toppling bus

19. CoG wedge
April 16, 2017
contact force of pivot
The point on an object where all its weight seems to be concentrated is called the centre of mass.
weight of wedge

20. The wedge is said to be in stable equilibrium.
April 16, 2017
If the wedge is slightly moved it will return to its original position.
The wedge is said to be in stable equilibrium.

21. The wedge is said to be in stable equilibrium.
April 16, 2017
If the wedge is slightly moved it will return to its original position.
The wedge is said to be in stable equilibrium.

22. April 16, 2017
Stable bottle

23. If the wedge is slightly moved it will topple over.
Unstable
April 16, 2017
If the wedge is slightly moved it will topple over.
The wedge is said to be in unstable equilibrium.

24. If the wedge is slightly moved it will topple over.
Unstable
April 16, 2017
If the wedge is slightly moved it will topple over.
The wedge is said to be in unstable equilibrium.

25. April 16, 2017
Unstable bottle

26. The cylinder is in neutral equilibrium.
Neutral stability
April 16, 2017
If the cylinder is slightly moved it will return stay in its new position.
The cylinder is in neutral equilibrium.

27. The cylinder is in neutral equilibrium.
Neutral stability
April 16, 2017
If the cylinder is slightly moved it will return stay in its new position.
The cylinder is in neutral equilibrium.

28. April 16, 2017
Neutral bottle

29. April 16, 2017
Task
Workbook page 106, Q2-4
Workbook page 105, Q6

30. Q4) The weight acts at the centre of mass =40 cm from the pivot
Q4) The weight acts at the centre of mass =40 cm from the pivot. The leg is 80- 5= 75 cm from the pivot Anticlockwise moment = clockwise moment 40 N x 0.4 m = F x 0.75 m 16Nm = F x 0.75m 16/0.75= F F = 21.3 N
April 16, 2017