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## Homework Statement

Problem 8.68

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 170 kg and is traveling east with a velocity of magnitude 5.10 m/s . Find the

*final velocity*of the car in each case, assuming that the handcar does not leave the tracks.

PartA

An object with a mass of 28.0 kg is thrown sideways out of the car with a speed of 2.40 m/s relative to the car's initial velocity.

PartB

An object with a mass of 28.0 kg is thrown backward out of the car with a velocity of 5.10 m/s relative to the initial motion of the car.

PartC

An object with a mass of 28.0 kg is thrown into the car with a velocity of 5.80 m/s relative to the ground and opposite in direction to the initial velocity of the car.

## Homework Equations

conservation of momentum?

M1V1+M2V2=M1V1+M2V2 (after)

## The Attempt at a Solution

I am unsure about how to approach these problems, should I use newtons second law? Or should I use conservation of momentum? I am use to using conservation of momentum when two objects collide, but not the opposite

Here is my attempt for Part A

M1=170

V1= 5.10

M2=28

V2=2.40

170(5.10) +28(5.10)=(170-28)V1 + 28(2.40)

I put 170-28 because after the object is thrown out of the cart the carts total mass should be less.

I would like to know if this approach is correct before I submit my answers