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Homework Help: Tension of strings in an elevator

  1. Apr 23, 2008 #1
    Two masses are connected by a string and are hanging from the ceiling of an elevator like this:

    [string 1]
    [4kg mass]
    [string 2]
    [6kg mass]

    Show the tension of each string in the following situations:
    i) Stationary
    ii) Moving up at 3m/s
    iii) Moving down at 3m/s
    iv) Moving up at 3m/s/s
    v) Moving down at 3m/s/s

    Ok, I am kinda stumped. Where do I start? Is there a formula for tension? Is it F=ma? Or F=m(9.8-a) or something?

    I'm just so horrible at physics, I'll be so grateful if someone could explain how this works..

    Thanks! :)
  2. jcsd
  3. Apr 23, 2008 #2
    You just need to look at the net force on each string. For example, you have two forces on the first string (weights of the hanging bodies). Other one is even easier. Remember the 1st Newton's law. That's when the elevator is stationary.

    The formula [itex]F=ma[/itex] can be used in part (iv) and (v). It's the inertial force. Just be aware of its direction.
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