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# Momentum2

## on May 12, 2011

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## Momentum2Presentation Transcript

• Learning Objectives
• Principle of Conservation of Momentum
In the absence of an external force, the total momentum of a system remains unchanged.
If no external force acts on a system, the total momentum before collision (or explosion) is equal to the total momentum after collision (or explosion)
or
Total momentum = Total momentum
before collision after collision
• Types of CollisionCase 1 : Elastic Collision
The colliding objects move separately after collision.
• u1
v1
v2
u2
m1
m2
m1
m2
Before collision After collision
Momentum :
m1u1 + m2u2 = m1v1 + m2v2
• Types of CollisionCase 2: Inelastic Collision
The colliding objects move together after collision.
• u1
v
u2= 0
m1
m2
m1 + m2
Before collision After collision
Momentum :
m1u1 + m2u2 = (m1 + m2)v
• Types of CollisionCase 3: Explosion
The objects involved are in contact with each other before explosion and are separated after the explosion.
• Before explosion
(m1 + m2), u = 0
(m1 + m2)u = m1 v1 - m2v2
v1
v2
m2
m1
After explosion
• Example 1
Car A Car B
Car A of mass 100 kg travelling at 30 m s-1 collides with Car B of mass 90 kg travelling at 20 m s-1 in front of it. Car A and B move separately after collision. If Car A is still moving at 25 m s-1 after collision, determine the velocity of Car B after collision.
• Example 2
Car A Car B
Car A of mass 100 kg travelling at 30 m s-1 collides with Car B of mass 90 kg travelling at 20 m s-1 in front of it. Car A is pulled by Car B with a velocity of 25 m s-1 after collision. Determine the common velocity of Car A and B after collision.
• Example 3
A bullet of mass 2 g is shot from a gun of mass 1 kg with a velocity of 150 m s-1 . Calculate the velocity of the recoil of the gun after firing.
• What have you learn today?
• Homework!! Smile 
Teks Book, page 75, no 1-10.
Submit: Next week before class.
Read subtopic THE CONSERVATION OF MOMENTUM this weekend