Momentum and Impulse

Momentum and Impulse

The momentum of an object is given by:                             Momentum = mass x velocity of the object                                            Momentum = mvNote: momentum is a vector quantity.The direction of the momentum is the same as that of the velocity.

Conservation of MomentumWhen two objects collide it can be shown that momentum is conserved provided there are no external forces applied to the system. For any collision:Total momentum of all objects before = total momentum of all objects after.

Elastic and Inelastic CollisionsAn elastic collision is one in which both kinetic energy and momentum are conserved. An inelastic collision is one in which only momentum is conserved.

Vector nature of momentumRemember momentum is a vector quantity, so direction is important. Since the collisions dealt with will act along the same line, then the directions can be simplified by giving:momentum to the right a positive sign and momentum to the left a negative sign.

ExplosionsA single stationary object may explode into two parts. The total initial momentum will be zero. Hence the total final momentum will be zero. Notice that the kinetic energy increases in such a process.

ImpulseAn object is accelerated by a force, F for a time, t. The unbalanced force is given by:                         F = ma = mv - mu/t Unbalanced force = change in momentum / time = rate of change of momentum                              Ft = mv - mu The term Ft is called the impulse and is equal to the change in momentum.

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