1. Last lesson Centre of gravity Stability

2. Centre of gravity The centre of gravity of an object is the point where the objects weight seems to act. With a uniform ruler, the C of G is at the mid-point. I think he wants you to copy this

3. More complex shapes How do you find the centre of gravity of more complex shapes? Complex shape man

4. Finding the centre of gravity i. Place a compass or needle through any part of the shape. ii. Make sure that the shape “hangs loose”. iii. Hang a plumb line on the needle. iv. After it has stopped moving, carefully draw a line where the plumb line is. v. Place the needle in any other part of the card. vi. Repeat steps ii to iv. vii. Where the two drawn lines cross is where the centre of mass is. viii. Physics is the most interesting science subject.

5. Stability

6. Stable objects have a wide base and a low centre of gravity. ¿Pueden ustedes copiar este por favor?

7. Robert Hooke

8. Investigating forces and springs You are going to investigate how much a spring stretches when a force is applied to it. The amount a spring stretches is called its extension. This is the difference in length between the stretched spring and the length of the spring when it was unstretched. (Remember we are looking at the force on the spring. A mass of 100g will have a weight (force of gravity pulling it down) of 1 Newton. Add masses to your spring and carefully measure its extension. You can do this until the spring breaks! (but you must wear goggles and be careful during this investigation). Your experimental report will include the following A table of results A graph of your results A conclusion describing what you have discovered (think about this!)

9. Table of results Force (N)Length of spring (cm) Extension (cm) 03.40 15.42 27.44 39.46

10. Graph Force (N) Extension (cm) Complete investigation for Weds 21 st October 1.Table of results 2.Graph 3.Two sentences of conclusion

11. Go!