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Homework Help: Center of Mass and Linear Momentum

  1. Mar 3, 2013 #1
    1.Two particles lie on an x axis, particle 1 at x = 1 m and particle 2 at x = 2 m. If you gradually increase the mass of particle 1, what happens to the center of mass of the two-particle system?

    2.If an external force acts on a system of several objects, can the external force change the net momentum of the system?

    2. Relevant equations

    3. The attempt at a solution
    I'm not sure for the first question if it moves in the negative or positive direction of x or if it does not move at all..
    Last edited: Mar 3, 2013
  2. jcsd
  3. Mar 3, 2013 #2


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    Staff: Mentor

    Just calculate the position for a small and a large mass of particle 1, and you will see what happens.
  4. Mar 3, 2013 #3
    Hi iAmKhanz

    You should be able to work this out without doing any calculations.
    Just think about what the centre of mass means
  5. Mar 3, 2013 #4
    i think i would think of the center of gravity of two objects on a teeter totter and use that to think of the the two objects one an x axis, . and which way the pivot point would have to move if one object increased its mass, . . don't take my word for it, its been a very long time since i was in school, . . but it also would seem that the center of mass and center of gravity if all objects were constant would be interchangable, . . If im wrong, . hopefully someone will correct me. . . . maybe i also misunderstood the question
  6. Mar 3, 2013 #5
    question 2 i would then think of two round objects sitting on the teeter totter both on the same side with it at rest and at zero momentum, . . then your finger "External Force" pushing down on the high empty side and seeing if the system changes momentum, ... . again, . its been a long time, and im not sure of all of the frame of reference as to your study, . if someone again will let me know if this is wrong or right i would appreciate it, .. not only for mfb's benefit, but also my own, . .thx
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