LAW OF CONSERVATION OF MOMENTUM

II. Conservation of Momentum

Collision/3 Laws

#22

Total Momentum
Before Interaction

Total Momentum
After Interaction

m₁v₁ + m₂v₂ = m₁v₁′ + m₂v₂′

Momentum is only conserved
in a totally elastic collision

Totally Elastic Collision?

What is the momentum

of the big fish after it

swallows the little fish?

-4 kgm/s

Total momentum before =
Total momentum after

Ex 4) What is the magnitude of the total momentum of these carts?

Total momentum = m₁v₁ + m₂v₂

Total mom. =

(4.0 kg)(3 m/s)+6.0kg(-3.0m/s)

= 12. kgm/s + -18. kgm/s

= -6.0 kgm/s

"Left train momentum

= 30 kgm/s.

What is the momentum

of the right train?"

What's the total momentum before the collision?

After the collision?

Answer: -30 kgm/s