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Homework Help: Torque and Tension Problems. How to answer these problems?

  1. Jan 19, 2014 #1
    1. The uniform beam shown in figure 5-15 weighs 500 N and supports a 700 N load. Find the tension in tie rope and the force of the hinge of the beam.

    The answer according to the book must be 2.9 kN as the tension in tie rope and 2.0 kN as the force of the hinge of the beam.

    2. The arm shown in figure 5-16 supports a 4.0 kg sphere. The mass of the hand and and forearm together is 3.0 kg and its weight acts at a point 15 cm from the elbow. Determine the force exerted by the biceps muscle.

    The answer according to the book is 0.13 kM which is the force exerted by the biceps muscle.

    3. The uniform, 120 N board shown in figure 5-19 is supported by two ropes as shown. A 0.40 kN weight is suspended one quarter of the way from the left end. Find FT1 (force of tension 1) and FT2 (force of tension 2) and the angle made by the left rope.

    The answer according to the book is 0.19 kN for FT1, 0.37 kN for FT2 and 14 degrees for the angle made by the left rope.

    I don't know how the book got these answers, so I need a full explanation and solution for these problems. As much as possible, make it step by step.

    Please help me! I'm an engineering student. I already looked at some examples, compared it and did the same process but it didn't match the book's answers.

    The following figures/diagrams are uploaded. Any answers will be accepted as much as it is correct and very well explained. Thank you!

    Attached Files:

  2. jcsd
  3. Jan 19, 2014 #2
    I cannot see any figures. The problems are phrased in such a way, that figures are required to understand them fully.

    Note that it is against the rules of the forum to solve problems for you. You need to show what you have done to solve them, then we could try and help you.
  4. Jan 19, 2014 #3
    I'm sorry sir. I attached the pictures, just check it out again. There are three photos (figures). I'll upload my solution later. My answer is actually wrong but it has the same place value. For example, the book's answer is 0.13 while I got 0.18. It's still wrong but I think I only mistook some parts of the solution.
  5. Jan 19, 2014 #4
    I suggest that you start with just one problem. When you figure out how to solve it, that may help you solve the others.
  6. Jan 19, 2014 #5


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    Staff Emeritus
    Science Advisor
    Homework Helper

    Well, you've got a much bigger problem, being an engineering student.

    You haven't shown any of your work in trying to solve these problems. The basic approach is to draw a free body diagram and use the equations of static equilibrium to solve for the unknown reactions.
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