Chapter 9: Impulse & Momentum
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Difference between collision and interaction
Interaction: A Force is exerted on a particle. Here the
duration of the force is not an important factor (for
example: frictional force)
Collision: An interaction for a very short period of
time (typically of the order of a millisecond)
Complete dynamics of a collision process could be
extremely complex but, the final outcome would
often be simple
For example, hitting a rubber ball, base ball etc.
In this chapter, we focus on the dynamics of
collisions
Typical process of a collision
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Consider a tennis ball being hit by a racquet
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Ball gets in contact with the rocket with initial velocity
(vix)
Ball and rocket stay together for a brief period of time
(~ ms)
The side of the ball that is in contact with the rocket
compresses
The side of the ball that is in contact with the rocket
expands and the ball finally leaves the rocket with new
final velocity (vfx)
Final outcome: The ball returns with a new velocity
due to a large force exerted by the racquet (NOTE: The
contact duration is very short)
Impulse (Visualization)
Fmax
Impulse: A large force acts for a very short time
(from dictionary !!!) 
Collision (Ball hitting a wall)
Equations of Motion
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From Newton’s second law F = ma
Momentum: A product of mass and
velocity of the particle
Example: Find Fmax if m=150g
Example: Find the maximum
height the ball after re-bounce?
m=100g
Conservation of Momentum