- #1

kraigandrews

- 108

- 0

## Homework Statement

Five hoboes, each with mass m, stand on a railway flatcar of mass M. They jump off one end of the flatcar with velocity u relative to the car. The car rolls in the opposite direction without friction.

(a) What is the final velocity of the flatcar if all the men jump at the same time?

Data: m = 78 kg; M = 280 kg; u = 3.3 m/s.

(b) What is the final velocity of the flatcar if they jump off one at a time? Does case (a) or case (b) yield the largest final velocity of the flat car? Can you give a simple physical explanation for your answer?

## Homework Equations

Pi=Pf

## The Attempt at a Solution

The answer for part a) is 4.596m/s

and for part b) i just use consveration of momentum starting with

0=-mu+(M+4m)v

v=(mu)/(M+4m)

then continuing on:

v=0.435 m/s

then the next one jumps:

m(0.435 m/s)=-mu+(M+3m)v

and just continuing this on until I get to where there is only one person left to jump and calculate the v, and they are the same, and the question seems to imply that they should not be the same. ideas? thanks.