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Homework Help: A mass of 30kg on a smooth horizontal table is tied to a cord running

  1. Mar 3, 2013 #1
    1. The problem statement, all variables and given/known data

    A mass of 30kg on a smooth horizontal table is tied to a cord running along the table over a frictionless pulley mounted at the edge of the table. A 10kg mass is attached to the other end of the cord. When the two masses are allowed to move freely the tension in the cord is

    can someone please check if the answer is 147 N?
    Because the solution given is 75N but I dont think I did anything wrong.
  2. jcsd
  3. Mar 3, 2013 #2
    You answer is incorrect. Show your working.
  4. Mar 3, 2013 #3
    (30)9.8) - T = (30) a
    + [ T - (10 (9.8) = 10a ]

    196 = 40a
    a= 4.9 m/s^2

    T - 98 = 10(4.9)
    T= 147N
  5. Mar 3, 2013 #4
    What forces act on the 30 kg mass? What forces on the 10 kg mass? What are the resultant accelerations?
  6. Mar 3, 2013 #5

    gravity force and tension force
    and acceleration i got is 4.9 , they have the same accleration because it is the same rope
  7. Mar 3, 2013 #6
    Gravity and tension act on the little mass. The big mass is on the table, so there is also the reaction force, which cancels the force of gravity on it.
  8. Mar 3, 2013 #7

    oh, so that will be the normal force?
  9. Mar 3, 2013 #8
    Of course.
  10. Mar 3, 2013 #9
    ok, thanks for ur help!
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