Impulse and Momentum

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

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

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

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

5. Impulse • In order to change the momentum of an object you must apply a force over some time interval. • Impulse = Force ´ time interval • = F t

6. Impulse and Momentum • Impulse = Change in Momentum • F Dt = mvf - mvi

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

8. Examples • Conservation of Momentum: If there are no external forces, the total momentum for a system remains unchanged. • Example 1: a person sitting inside a car pushing against the dashboard • Example 2: a bullet fired from a rifle • Example 3: a rocket in space • m1u1 + m2u2 = m1v1 - m2v2

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