1.To understand what momentum is 2.To understand conservation of momentum and to be able to complete related calculations 3.To understand different types of collision, to be able to complete related calculations and to be able to classify a collision as either elastic or inelastic Book Reference : Pages 4-17

Which is more effective at demolishing a wall? A 1kg metal ball moving at 50ms -1 Or a 1000kg ball moving at 1ms -1 Newton realised that what happens to a moving objects involved in a collision depends upon two things : Mass of the object Mass of the object Velocity of the object Velocity of the object

Newton used the concept of momentum to explain the results of collisions Momentum = mass x velocity p = m v Units : p (kg ms -1 ) = m (kg) x (ms -1 ) Note since velocity is a vector quantity, (both magnitude and direction) then momentum is also a vector quantity

When objects collide, assuming that there are no external forces, then momentum is always conserved.... Definition : When two or more objects interact, the total momentum remains constant provided that there is no external resultant force Mass 75 kg Velocity 4 ms -1 Mass 50 kg Velocity 0 ms -1 Mass 125 kg Velocity ??? ms -1

When objects hit each other the resulting collision can be considered to be either elastic or inelastic. Momentum and total energy are always conserved in both cases. Elastic : momentum conserved, kinetic energy conserved, total energy conserved Inelastic : momentum conserved, kinetic energy NOT conserved, total energy conserved In an Inelastic collision some of the kinetic energy is converted to other forms of energy (often heat & Sound)

Is the following collision elastic or inelastic? A toy lorry of mass 2kg is travelling at 3ms -1 and crashes into a smaller a toy car with a mass of 800g which is travelling at 2 ms -1 in the same direction as the lorry. The velocity of the lorry after the collision is 2.6 ms -1. What is the velocity of the car after the collision and is the crash elastic or inelastic?

Mass 2 kg Velocity 3 ms -1 Mass 800 g Velocity 2 ms -1 Mass 800g Velocity ? ms -1 Mass 2 kg Velocity 2.6 ms -1 Lorry Momentum = 2 x 3 Lorry Momentum = 6 kgms -1 Car Momentum = 0.8 x 2 Car Momentum = 1.6 kgms -1 Total momentum before = 7.6 kgms -1 Total momentum after= 7.6 kgms -1 Lorry Momentum = 2 x 2.6 Lorry Momentum = 5.2 kgms -1 Car Momentum = Total - Lorry Car Momentum = 7.6 – 5.2 Car Momentum = 2.4 kgms -1 Car Momentum = 0.8v  v = 2.4 / 0.8 = 3 ms -1

Mass 2 kg Velocity 3 ms -1 Mass 800 g Velocity 2 ms -1 Mass 800g Velocity 3 ms -1 Mass 2 kg Velocity 2.6 ms -1 Lorry E k = ½ x 2 x (3) 2 Lorry E k = 9J Car E k = ½ x 0.8 x (2) 2 Car E k = 1.6J Total E k before = 10.6J Lorry E k = ½ x 2 x (2.6) 2 Lorry E k = 6.76J Car E k = ½ x 0.8 x (3) 2 Car E k = 3.6J Total E k after= 10.36J Total E k before  Total E k after  Inelastic Collision Where is the energy likely to have gone?

Two trolleys on an air track are fitted with repelling magnets. The masses are 0.1kg and 0.15kg respectively. When they are released the lighter trolley moves to the left at 0.24ms -1. What is the velocity of the heavier trolley A ball of 0.6kg moving at 5ms -1 collides with a larger stationary ball of mass 2kg. The smaller ball rebounds in the opposite direction at 2.4ms -1 Calculate the velocity of the larger ball Is the Collision elastic or inelastic. Explain your answer