A railroad handcar is moving along straight, frictionless tracks with negligible

Question

A railroad handcar is moving along straight, frictionless tracks with negligible air resistance. In the following cases, the car initially has a total mass (car and contents) of 200kg and is traveling east with a velocity of magnitude 5.50m/s . Find the final velocity of the car in each case, assuming that the handcar does not leave the tracks.

Part B

An object with a mass of 25.0kg is thrown backward out of the car with a velocity of 5.50m/srelative to the initial motion of the car.

Part C

An object with a mass of 25.0kg is thrown into the car with a velocity of 6.10m/s relative to the ground and opposite in direction to the initial velocity of the car.

Explanation / Answer

b)

Initial momentum of car = 200*5.5 = 1100 kg.m2

velocity of 25 kg mass relative to car = 5.5 m/s

So, velocity of the mass relative to ground = 5.5 - 5.5 = 0 m/s

So, momentum of the 25 kg mass = 25*0 = 0 kg.m2

So, remaining of the mass of car = 200 - 25 = 175 kg

So, let the speed of the car now, be v

So, now, the moemtum of car = 175*v

But, by conservation of momentum, 175*v - 25*0 = 200*5.5

So, v = 6.28 m/s east <---------answer

c)

Similar conservation of momentum yeilds,

175*v - 25*6.1 = 200*5.5

So, v = 7.2 m/s <--------answer

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