Momentum = mass x velocity

The formula to find the momentum of an object:

• p = mv

where p represents the object's momentum

where m represents the object's mass

where v represents the object's velocity

Example 1: A car of mass 50kg travels towards the east at a velocity of 30m/s. What is its momentum?

Remember: Since the object is going to the east we give the velocity a positive sign.

p = mv

p = 50 kg x 30 m/s

p = 1500 kgm/s Answer

Example 2: A car of mass 40kg travels towards the west at a velocity of 20m/s. What is its momentum?

Remember: Since the object is going to the west we give the velocity a negative sign.

p = mv

p = 40 kg x -20 m/s

p = -800 kgm/s Answer

The law of conservation of momentum states that the total momentum before collision is equal to the total momentum after collision in the absence of external forces.

The equation for the law of conservation of momentum:

Total Momentum Before = Total Momentum After

Elastic Collisions

1. Momentum Conserved and Kinetic Energy Conserved
2. Objects do not stick together after the collision

The law of conservation of momentum equation for Elastic Collisions :

m1u1 + m2u2 = m2v1 +m2v2

m1 - mass of object 1

m2 - mass of object 2

u1 - initial velocity of object 1

u2 - initial velocity of object 2

v1 - final velocity of object 1

v2 - final velocity of object 2

Inelastic Collisions

1. Momentum Conserved but Kinetic Energy IS NOT Conserved
2. Objects stick together and "move as one" after the collision

The law of conservation of momentum equation for Elastic Collisions :

m1u1 + m2u2 = (m1+m2)v

m1 - mass of object 1

m2 - mass of object 2

u1 - initial velocity of object 1

u2 - initial velocity of object 2

v - final velocity of object 1 and object 2 [Remember: Since they stick together they move with the same velocity]