# Taylor mechanics ch3 problem7 -- Men jumping off of a railcar

1. Oct 16, 2016

### kylinsky

1. The problem statement, all variables and given/known data
two man,each of equal mass m,are standing at one end of a stationary railroad flatcar with frictionless wheel and mass mcar.Find the car's speed if the two men run to the other end of the car and jump off simultaneously with the same speed u(relative to the car)
2. Relevant equations

3. The attempt at a solution
let vh be the men's speed relative to the ground at the instant they jump off the car.Thus
u= vh+vcar.Since the momentum of the system is conservative,2mvh=mcarvcar

After solving the equations,i got (2mu)/(2m+mcar) ,but i found a different answer from mine on the websitehttp://chriskranenberg.wix.com/taylor-mechanics-solutions.I want to make sure which one is right

Last edited by a moderator: Oct 16, 2016
2. Oct 16, 2016

### Staff: Mentor

Why don't you type out the web site solution instead of forcing helpers to go searching for a pdf offsite? It can only be a few characters long. You're asking for help, so make it easier for the helpers to do so.

You posted an identical question by a slightly different name on October 8th:

taylor mechanics chap3,problem 4

and you never followed up the help response (although you did fix the notation/formatting in your post). I'll give the same advice this time: Show your work so that we can help you with that. We won't just select the right answer for you.

3. Oct 16, 2016

### kylinsky

i did follow the help response and add the derivation to my solution.

Last edited by a moderator: Oct 16, 2016
4. Oct 16, 2016

### Staff: Mentor

5. Oct 16, 2016

### Staff: Mentor

So getting back to the problem at hand, your work as far as it is described is correct, and I agree with your solution.

I won't comment on work I can't see, and I don't feel the urge to download a pdf from some site to go hunting for this alternate solution somewhere inside it. If you wish to discuss this alternate solution, please present it here in detail, or at least post an excerpted image of the specific content.