2. Momentum Does momentum make you feel like this? Its not so bad, start with this calculation.. What is the momentum if the mass is 13.5kg and the velocity 0.8m/s? 14 th January UNITS!!!

3. The Answer 10.8 kgm/s See calculating momentum is easy when you are given the mass and velocity. Lets see how momentum can be calculated for collisions and objects moving apart like in explosions.

4. The Main Rule So the total momentum after collision or explosion must be the same as before.

5. Conservation of Momentum When doing problems involving collisions or explosions, just work out the momentum at the start and equate it with the momentum at the end. Principle of conservation of momentum: for a system of interacting objects, the total momentum remains constant, provided no external resultant force acts on the system. In English, this means: total momentum before = total momentum after 29 October 2015

6. Worked example A sheep of mass 100kg is out for a run one day. He picks up speed until he reaches 8ms -1, when he runs into a stationary shopping trolley of mass 20kg. The force of the impact slows our sheep to 6ms -1, and causes the trolley to start moving. What is the velocity of the trolley immediately after impact? Sheep: m s = 100kg u s = 8m/s v s = 6m/s Trolley: m t = 20kg u t = 0m/s Total initial momentum = initial momentum of sheep + initial momentum of trolley = (100 x 8) + (20 x 0) = 800kgm/s Total final momentum = final momentum of sheep + final momentum of trolley = (100 x 6) + (20 x v t ) = 600 + 20v t Using principle of conservation of momentum: 800 = 600 + 20v t v t = 10m/s 29 October 2015

7. A gun firing a bullet The gun has a mass of 1 kg The bullet has a mass of 0.01kg The velocity of the bullet is 150 m/s The total momentum before firing the gun is 0 Calculate the momentum of the bullet. How can we find the velocity of the gun?

8. A gun firing a bullet The gun has a mass of 1 kg The bullet has a mass of 0.01kg The velocity of the bullet is 150 m/s The total momentum before firing the gun is 0 The momentum of the bullet = 1.5 kgm/s The momentum of the gun must be = - 1.5 kgm/s So the velocity of the gun ….. 1.5/1 = 1.5 m/s * Negative value show opposite direction

9. How does a cars safety features protect you in car crash?