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Homework Help: Calculate the acceleration of the system

  1. Mar 8, 2006 #1
    Two crates, of mass m1 = 60 kg and m2 = 130 kg, are in contact and at rest on a horizontal surface (Fig. 4-54). A 620 N force is exerted on the 60 kg crate. The coefficient of kinetic friction is 0.15.

    (a) Calculate the acceleration of the system.
    m/s2 (to the right)
    (b) Calculate the force that each crate exerts on the other.
    (c) Repeat with the crates reversed. acceleration m/s2
    crate force N

    I'm trying to caculate the acceleration and I cant seem to get it. I tried this but I know it is incorrect:


    .15 * (60*9.8) - .15 *(130*9.8)= -102.9

    Can someone tell me where I'm going astray?
  2. jcsd
  3. Mar 8, 2006 #2


    User Avatar
    Science Advisor
    Gold Member

    \mu_{k} mg
    is not your acceleration. It is the force exerted by kinetic friction. It opposes the 620 N force applied to the 60 kg crate.
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