Key Areas covered Conservation of momentum in one

Key Areas covered • Conservation of momentum in one dimension and in cases where the objects may move in opposite directions.

What we will do today • State that momentum is the product of mass and velocity. • State the law of conservation of linear momentum.

Momentum

Momentum is a vector quantity and is the product of mass and velocity. Momentum = mass x velocity kg ms-1 The units of momentum are kgms-1. Momentum is sometimes given the symbol p. p = mv The direction of the momentum is the same as the velocity.

Experiment • • Aim: To find our own momentum Results: Distance travelled m Time taken s Your Velocity (d/t) m/s Your mass kg Your momentum (mv) kgm/s

Virtual Experiment – Law of Conservation of Momentum • • • Click link below Select Mechanics and Properties of Matter Run Collisions and Explosions Use Inelastic collision; elastic collisions; and explosions • Record results on table (next slide) • Virtual Higher Physics

Virtual Experiment – Law of Conservation of Momentum Before After m 1 v 1 m 2 v 2 1 x 2=2 1 x 0=0 1 x 1=1 2 x 3=6 1 x 0=0 2 x 1=2 1 x 4=4 2 x 0=0 1 x 0=0 2 x (-2)= -4 1 x 4=4

Conclusion Momentum is always conserved in collisions. However, this will only be the case if the direction of momentum is taken into account.

The Law of Conservation of Momentum In any collision or explosion free of external forces, the total momentum remains the same. This can be applied to the interaction of two objects moving in one dimension, in the absence of net external forces. • For any collision (with no external forces): Total momentum of = Total momentum of all objects before all objects after

Example Solution 5 ms-1 3 kg 5 ms-1 2 kg + ve Tot mom Before = Tot mom After Find the velocity of m 1 v 1 + m 2 v 2 = m 3 v 3 the trolleys when (3 x 5) + (2 x -5)= (3 + 2) v 3 they stick together 15 + (-10) = 5 v 3 after colliding. v = 5/5 v = 1 ms-1 to right