1. The Turning Effect of Forces You should be able to: state what the centre of gravity of an object is. describe a simple experiment to determine the centre of gravity of an object. define and apply the moment of force. apply the principle of moments to solve problems, including the human forearm.

2. The Turning Effect of Forces 1. Suspend object from a point 2. Use plumb line to find the vertical line and mark it on with a pencil 3. Hang from another point and draw another vertical line 4. Where the lines intersect gives position of centre of gravity 5. Check your centre of gravity by choosing another point and repeating. Describe an experiment to find the centre of gravity of an object.

3. The Turning Effect of Forces Centre of Gravity – the point where the weight of an object can be considered to act.

4. The Turning Effect of Forces Centre of Gravity

5. The Turning Effect of Forces Define and apply the moment of force

6. The Turning Effect of Forces Define and apply the moment of force

7. The Turning Effect of Forces Define and apply the moment of force

8. The Turning Effect of Forces Define and apply the moment of force

9. The Turning Effect of Forces Define and apply the moment of force Use the equipment available to find ; 1)The mass of the rule 2)The mass of the unknown weight

10. The Turning Effect of Forces Define and apply the moment of force

11. The Turning Effect of Forces Define and apply the moment of force

12. The Turning Effect of Forces Define and apply the moment of force

13. The Turning Effect of Forces You should be able to: define and apply the torque of a couple explain that both the net force and net moment on an object in equilibrium is zero apply the principle of moments to solve problems where the perpendicular force has to be calculated.

14. Couple The Turning Effect of Forces

15. What is the significance of this diagram ?

16. The Turning Effect of Forces 60 o 70 kg W 5 m 3 m What is the counterweight (W) required to balance the light crane arm shown in diagram ?

17. The Turning Effect of Forces What is the tension (T) in the cable shown in diagram ? 20 N 3 m 1.5 m T 70 o

18. The Turning Effect of Forces T 25 m 20 m 65 o 70 N What is the tension (T) in the cable shown in diagram?

19. Typical loading diagram