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# P5d Momentum

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### P5d Momentum

1. 1. P5d - Momentum Collisions , crashes and cannons
2. 2. P5d - Momentum <ul><li>Opposite reaction forces </li></ul><ul><li>When one body exerts a force on a second body, the second body exerts an _________ and ____________ force on the first </li></ul><ul><li>In other words: If you push something, it pushes back just as hard </li></ul>“ For every action, there is an equal and opposite reaction .” Isaac Newton
3. 3. Spot the action & reaction forces!
4. 4. Spot the action & reaction forces! beam 10 kg
5. 5. Spot the action & reaction forces!
6. 6. Spot the action & reaction forces!
7. 7. Opposite reaction forces
8. 8. Opposite reaction forces
9. 9. Forces and momentum revision <ul><li>If forces are balanced… </li></ul><ul><li>If forces are unbalanced… </li></ul><ul><li>Forces and velocities are vectors and must have… </li></ul><ul><li>Momentum = </li></ul>
10. 10. Momentum <ul><li>Q ~ What would do more damage: a 6 kg bowling ball traveling at 6 m/s or a 10 g ping-pong ball traveling at 6 m/s? </li></ul>
11. 11. What’s the momentum? <ul><li>A 20000 kg elephant charging at 10 m/s </li></ul>
12. 12. What’s the momentum? <ul><li>Lewis Hamilton’s 400 kg car traveling at 80 m/s </li></ul>
13. 13. What’s the momentum? <ul><li>A 6 kg bowling ball traveling at 6 m/s </li></ul>
14. 14. What’s the momentum? <ul><li>A 10 g ping-pong ball traveling at 6 m/s </li></ul>
15. 15. Collisions <ul><li>There is no change in momentum during a collision - momentum is always conserved </li></ul><ul><li>P total(before) = P total(after) = 0 </li></ul><ul><li>P red(before) + P blue(before) = P red(after) + P blue(after) = 0 </li></ul>
16. 16. Recoil <ul><li>Many guns and cannons recoil when fired </li></ul><ul><li>P total(before) = P total(after) = 0 </li></ul><ul><li>P gun(before) + P bullet(before) = P gun(after) + P bullet(after) = 0 </li></ul>
17. 17. Explosions - Total momentum is zero
18. 18. Preventing injury
19. 19. Preventing injury in crashes <ul><li>Seatbelts, airbags and crumple zones are all safety features of cars </li></ul><ul><li>They reduce the risk of injury in the event of a crash </li></ul><ul><li>They do this by slowing the collision down… </li></ul>
20. 20. Slowing collisions down <ul><li>Force = change in momentum </li></ul><ul><li> time </li></ul>