1. SPRINGS Stretching and bouncing !

2. 2 Snake in a box As the tin opens the snake pops out as the spring is released. What is inside? snake spring

3. 3 Stetching Pull Pull harder hold

4. 4 Stop pulling and --- Elastic materials spring back into shape. Plastic materials stay stretched. (Like plasticine)

5. 5 Lets find out - - -

6. 6 Stretchimals have different shapes Thick Thin Long Short

7. 7 They are stretchy You can pull them.

8. 8 Try Different forces on a stretchimal What happens?

9. 9 Forces on a stretchimal Before a force is applied - flat on table 10 newton force on stretchimal What would happen with a smaller force? a larger force?

10. 10 Forces are measured in newtons The weight of an apple is about 1 newton. The weight of a bag of sugar is 10 newtons. When you stand on the floor it is pushing up with a force of about 40 newtons.

11. 11 Stretchimals Different shapes Same force What will happen?

12. 12 Forces on stretchimals What shape has the blue lizard, when stretched? Before a force is applied Flat on a table 10 newtons

13. 13 Now for some tests !

14. 14 Re-cap Different forces on the same elastic –  The larger the force- the larger the stretch Same force on different stretchimals-  the fatter the stretchimal- the smaller the stretch

15. 15 SPRINGS

16. 16 Toys with springs The spring bends as the woodpecker pecks down the rod.

17. 17 Springs are often hidden Look around you. paper clip spring

18. 18 Beds often have springs The springs are compressed when you lie on them but are strong enough to support you. Why must this be a very hard bed !

19. 19 Springs are useful Forces

20. 20 Springs save lives Blood must flow through our hearts. The blood flows through arteries Arteries become blocked Springs can be used to keep hearts working. Stents can be squeezed - later the stent will open. A stent ( enlarged)

21. 21 Placing a stent in an artery 1. The squeezed stent is placed at the blockage. 2. A balloon opens the stent. 3. The stent keeps the artery open so the blood can flow. Step 1 Step 2 Step 3 Images © Salinas Valley Memorial Healthcare

22. Forces can do amazing things! Science saves lives