The document discusses different types of collisions between objects. In an elastic collision, both momentum and kinetic energy are conserved. In an inelastic collision, momentum is conserved but kinetic energy is not. In a perfectly inelastic collision, momentum is conserved and kinetic energy is not conserved, and the objects stick together after collision and move with the same final velocity. Momentum is conserved in all collision types.

1. Collision
Dr.Sreekala C O

2. Conservation of Momentum
 In an isolated and closed system,
the total momentum of the
system remains constant in time.
 Isolated system: no external forces
 Closed system: no mass enters or
leaves
 The linear momentum of each
colliding body may change
 The total momentum P of the system
cannot change.
April
12,
2023

3. Conservation of Momentum
 Start from impulse-momentum
theorem
 Since
 Then
 So
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12,
2023
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4. Conservation of Momentum
 When no external forces act on a system consisting of
two objects that collide with each other, the total
momentum of the system remains constant in time
 When then
 For an isolated system
 Specifically, the total momentum before the collision
will equal the total momentum after the collision
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5. Types of Collisions
 Momentum is conserved in any collision
 Inelastic collisions: rubber ball and hard ball
 Kinetic energy is not conserved
 Perfectly inelastic collisions occur when the objects
stick together
 Elastic collisions: billiard ball
 both momentum and kinetic energy are conserved
 Actual collisions
 Most collisions fall between elastic and perfectly
inelastic collisions
April
12,
2023

6. More About Elastic Collisions
 Both momentum and kinetic energy
are conserved
 Typically have two unknowns
 Momentum is a vector quantity
 Direction is important
 Be sure to have the correct signs
 Solve the equations simultaneously
April
12,
2023
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

7. Elastic Collisions
 A simpler equation can be used in place of the KE
equation
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12,
2023
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8. More about Perfectly Inelastic
Collisions
 When two objects stick together
after the collision, they have
undergone a perfectly inelastic
collision
 Conservation of momentum
 Kinetic energy is NOT conserved
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2023
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9. Collisions Summary
 In an elastic collision, both momentum and kinetic energy
are conserved
 In a non-perfect inelastic collision, momentum is conserved
but kinetic energy is not. Moreover, the objects do not stick
together
 In a perfectly inelastic collision, momentum is conserved,
kinetic energy is not, and the two objects stick together
after the collision, so their final velocities are the same
 Elastic and perfectly inelastic collisions are limiting cases,
most actual collisions fall in between these two types
 Momentum is conserved in all collisions
April
12,
2023

10. Summary of Types of Collisions
 In an elastic collision, both momentum and kinetic
energy are conserved
 In an inelastic collision, momentum is conserved but
kinetic energy is not
 In a perfectly inelastic collision, momentum is
conserved, kinetic energy is not, and the two objects
stick together after the collision, so their final
velocities are the same
April
12,
2023
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