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Help with Homework Please Thankyou!

  1. Sep 24, 2008 #1
    1. A black of mass 5.59 kg lies on a frictionless horizontal surface. The block is connected by a cord passing over a pulley to another block of a mass 4.8 kg which hangs in the air, as shown on the following picture. Assume the cord to be light(massless and weightless) and unstretchable and the pulley to have no friction and no rotational inertia. The acceleration of gravity is 9.8 m/s 2



    2. I tried to use F=ma 47.04=5.59a



    3. Wrong answer 8.41 m/s 2

    [​IMG]

    Also Calculate the tension in the cord. Answer in units of N
    Tried answer 47.04 N
     
  2. jcsd
  3. Sep 24, 2008 #2
    2. A light, inextensible cord passes over a light, frictionless pulley with a radius of 8.3 cm. It has a(n) 19 kg mass on the left and a(n) 7.9 kg mass on the right, both hanging freely. Initially their center of masses are a vertical distance 2.6m apart The acceleration of gravity is 9.8 m/s 2

    2A. At what rate are the two masses acceleration when they pass each other? Answer in units of m/s 2
    3. Already found the answer 4.04 m/s 2. Thought it might help with second question.

    2B. What is the tension in the cord when they pass each other? Answer in units of N.
    3. Wrong answer: 44.844 N

    [​IMG]
     
  4. Sep 24, 2008 #3
    3. A block is releases from rest on an inclined plane and moves 3.1 m during the next 3.9 s. The acceleration of gravity is 9.8 m/s


    2a. What is the magnitude of the acceleration of the block? Answer in units of m/s 2?

    3. Correct Answer 0.4076 m/s2



    2b. What is the coefficient of kinetic friction μk fro the incline?

    [​IMG]
     
  5. Sep 24, 2008 #4

    hage567

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    The force is not going to be 47.04 N. You must write out the forces on each mass. You will get two equations and you need both to solve this problem.
     
  6. Sep 24, 2008 #5

    hage567

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    It would help if you would show HOW you got your answers. Then we can point out where you're going wrong.
     
  7. Sep 24, 2008 #6

    hage567

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    So what have you tried for 2b? You need to show what you've done before we can help.
     
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