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Homework Help: Velocity problem

  1. Sep 25, 2005 #1
    a boat is moving at 3 meters/sec one boy wieghs 65 kgjumps off the front at 2 m/s. the second boy jumps out of the back of the boat, he wieghs 68kg and jumps at a speed of 4 m/s. if the boats mass is 100kg. what is the velocity of the boat.

    what i did was multiply 65 times 2 to get the force that the 1st bot jumped of the boat a. i got 130kg m/s. then i did the same for the second boy but i used 68 and 4 and got 272kg m/s. i subracted 130 from 272 and got 142. after that i added up the masses of the two boys and got 133. i divided 142 by 133 and got 1.06 i added the initial 3 m/s and got 4.06. Is this right? it seemed too easy.
    Last edited: Sep 25, 2005
  2. jcsd
  3. Sep 25, 2005 #2
    (mass X velocity) is momentum, not force.

    Did they give you the mass of the boat?
  4. Sep 25, 2005 #3
    no it wasn't given
  5. Sep 25, 2005 #4
    ooops the boat was 100 kg.
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