Four friends jump from a raft

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Homework Statement


Suppose your three friends and you are on a square shaped raft. You all have jumped mutually perpendicularly into the river from the raft at velocity 2m/s at the same time. What will be the velocity of the center of mass of the raft?

Homework Equations


Maybe,the law of conservation of momentum will help.

The Attempt at a Solution


Not sure how to do that,because the mass of the four guy and the raft isn't mentioned.So how can I deal with it?
 

Answers and Replies

  • #2
mjc123
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Maybe there's a clue there. Think about the symmetry of the problem.
 
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Orodruin
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Not sure how to do that,because the mass of the four guy and the raft isn't mentioned.
The implied assumption is likely that your mass is the same as that of your friends, you can call it ##m##. The raft mass you can call ##M##.
 
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  • #4
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The implied assumption is likely that your mass is the same as that of your friends, you can call it ##m##. The raft mass you can call ##M##.
But what's next?There's two dimensional motion here as the angle is mentioned.So how can I proceed?
 
  • #5
Orodruin
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What is the momentum carried away by each jumper? What does it mean for the momentum of the raft?
 
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Please tell me in detail.As you can see that the motion of the friends is not confined in a straight line,but in four different sides.
 
  • #7
Orodruin
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Please tell me in detail.As you can see that the motion of the friends is not confined in a straight line,but in four different sides.
I am fully aware of this and I am asking you a direct question. Answering that question instead of asking to be spoon-fed will bring you closer to the answer. Nobody here is going to solve the problem for you, that would be against forum rules, which you agreed to when you signed up.
 
  • #8
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Theres a reason i love mechanics so much ,and that is the fact that a picture can tell more than a thousand words !

Well if i were you ,id sketch out(like make diagram ,not actually make an artsy sketch !) the events taking place in the problem and then make observations and write out a few equations

Once you answer the questions asked by Orodruin it shall easily lead you the answer,i assure you.

And yea 'tis implied that that all four men have same mass.


[Note : i just realised that you are a new member , and whrn i was new to the site ,i was really confused when helpers asked me questions like "what does
this imply and what does that imply" at first i thought they were asking for clearification of the question and i was rather confused ,

but in actuality those questions (and the answers to them) lead one to the answer.


After all tis much better if one finds an answer rather than being given an answer !]
 
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