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Homework Help: Torque and Kinematics q

  1. Nov 5, 2006 #1
    hey all, im having prob with two questions,

    the first one goes like this.

    "two scales are separated by 2.00 m, and a plank of mass 4.00 kg is placed between them. each scale is observed to read 2.00 kg. a person now lies on the plank, after which the right scale reads 30.0 kg and the left scale reads 50.0 kg. how far from the right scale is the person's center of gravity located?"

    the answer is either 1.25m, or 1.26m, depending on if you ommited the mass of the table or not. I didn't and got 1.26m

    and a kinematics question i need help with

    A 25 N force acts on a 3.5 kg mass acceleration it in a location where the friction between the cart and the surface is 4.8 N. What is the velocity of the cart after it has traveled 12.6 m?

    i got 12.1 but not sure if its correct

    any help would be appreciated

    thanks =D

    edit my work:

    for the first problwm

    sum y = 0
    (50g + 30g) - (f person + 4g) = -
    f person = 744.8N

    sum t = 0
    rf + rf - rf = 0
    (744.8n)(x) + (4g)(1m) - (2m)(50g) = 0
    x = 1.26m

    second problem:

    a = 5.7 m/s^2
    d = .5at^2
    t = 2.1 s
    v = at
    v = 11.9 m/s
    Last edited: Nov 5, 2006
  2. jcsd
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