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Horizontal Pulley Question [Forces]

  1. Oct 21, 2013 #1
    1. The problem statement, all variables and given/known data

    An object is hanging by a [mass-less] string on a [mass-less] pulley from a cart on a desk with a mass of 1.8 kg. The cart has an acceleration of 2.5 m/s^2. Calculate the mass of the hanging object given that:

    a) There is no friction.
    b) There is a frictional force of 0.4 N on the wheels of the cart.

    2. Relevant equations

    Fnet = ma

    3. The attempt at a solution

    m1 = 1.8 kg
    a = 2.5 m/s^2
    m2 = ?

    I don't know where to start with this question...
    Maybe Fnet = (1.8 kg)(2.5 m/s^2) = 4.5 N ? But what would I do with this.
    ... I don't know.
  2. jcsd
  3. Oct 21, 2013 #2
    What do you think the acceleration of the falling object is?
  4. Oct 21, 2013 #3
    Isn't it the same?
  5. Oct 21, 2013 #4
    Perhaps, think about a force diagram. You have one force going downward and one upward. Draw it out, then solve for your unknown.
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