Elastic and Inelastic Collision

Elastic Collision

Elastic collision is the collision where the kinetic energy is conserved after the collision.

Total Kinetic Energy before Collision
= Total Kinetic Energy after Collision

Additional notes:

• In an elastic collision, the 2 objects separated right after the collision, and
• the momentum is conserved after the collision.
• Total energy is conserved after the collision.
  

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Inelastic Collision

Inelastic collision is the collision where the kinetic energy is not conserved after the collision.

Additional notes:

• In a perfectly elastic collision, the 2 objects attach together after the collision, and
• the momentum is also conserved after the collision.
• Total energy is conserved after the collision.
  

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Example 1 - Perfectly Inelastic Collision

A lorry of mass 8000kg is moving with a velocity of 30 ms^-1. The lorry is then accidentally collides with a car of mass 1500kg moving in the same direction with a velocity of 20 ms^-1. After the collision, both the vehicles attach together and move with a speed of velocity v. Find the value of v.

Answer:

(IMPORTANT: When 2 object attach together, they move with same speed.)

m₁ = 8000kg
m₂ = 1500kg
u₁ = 30 ms^-1
u₂ = 20 ms^-1
v₁ = v
v₂ = v

According to the principle of conservation of momentum,

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂
(8,000)(30) + (1,500)(20) = (8,000)v+ (1,500)v
270,000 = 9500v
v = 28.42 ms^-1

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External Link
HyperPhysics - Elastic and Inelastic Collision
Types of Collision

Interactive Animation
Elastic and Inelastic Collision 1 - Java Applet
Collision on an Air Track - Flash Animation
Elastic and Inelastic Collision 2- Java Applet