Arailroad car with a mass of 11 000 kg collides and couples with a second car of mass 19 000 kg that is initially at rest. the first car is moving with a speed of 4.5 m/s prior to the collision. a. what is the initial momentum of the first car? b. if external forces can be ignored, what is the final velocity of the two railroad cars after they couple?

a) 49500 Kg.m/s

b)  1.65 m/s

Explanation:

Given:

Mass of the car, m₁ = 11000 kg

Mass of the second car, m₂ = 19000 kg

Initial Speed of the first car, u₁ = 4.5 m/s

Initial velocity of the second car , u₂ = 0

Now,

Momentum = Mass × Velocity

Initial momentum = m₁u₁

Thus

Initial momentum P₁ = 11000 × 4.5 = 49500 kg-m/sec

b)By using the concept of momentum conservation

Initial momentum = Final momentum

m₁u₁ + m₂u₂ = ( m₁ + m₂ )v

Where, v is the velocity after collision

thus,

49500 + 19000 × 0 = ( 11000 + 19000 ) × v

or

V =

or

v = 1.65 m/s

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.