Impulse and Momentum Dr Ajay Kumar Professor School

Impulse and Momentum Dr Ajay Kumar Professor School of Physical Education DAVV Indore

Momentum and Collisions l This chapter is concerned with inertia and motion. Momentum helps us understand collisions. l Elastic Collisions - objects rebound l Inelastic Collisions - object stick together an usually become distorted and generate heat

Momentum l Momentum = mass ´ velocity l p = mv l Momentum is a vector quantity.

l A large truck has more momentum than a car moving at the same speed because it has a greater mass. l Which is more difficult to slow down? The car or the large truck? l Large Momentum Examples: – Huge ship moving at a small velocity – High velocity bullet

Impulse l In order to change the momentum of an object you must apply a force over some time interval. l Impulse = Force ´ time interval l = Ft

Impulse and Momentum l Impulse = Change in Momentum l l F Dt = mvf - mvi

Conservation of Momentum l This means that the momentum doesn’t change. l Recall that F t = D(mv) l In this equation, F is the "external force". l Internal forces cannot cause a change in momentum.

Examples l Conservation of Momentum: If there are no external forces, the total momentum for a system remains unchanged. l Example 1: a person sitting inside a car pushing against the dashboard l Example 2: a bullet fired from a rifle l Example 3: a rocket in space l m 1 u 1 + m 2 u 2 = m 1 v 1 - m 2 v 2

Coefficient of Restitution l For perfectly elastic collisions e=1. l If the two object stick together, e=0. l Otherwise 0<e<1.