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Physics

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A person holds an object of mass m = 4.2 kg on the palm of the hand with the arm stretched. Use the torque equilibrium equation to determine the magnitude of the force F exerted by the biceps muscle when a = 25 cm, b = (0.15 · a), and the angle θ = 75°. Neglect the weight of the lower arm

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    (a+b)(Fg)-b(Fcosθ) = 0
    -->solve for F

    Have you done #1 or #3 of the assignment? If you have, please help!

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    No but I am going crazy trying to do the calculations! Grr...wish I had more time to review before doing this h/w!

    Thanks though. If I figure it out i'll post back here, ok

  • Physics -

    Hey Anna, can you break that down. I'm so confused!

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    Fg in the eqn she gave is mg...

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    Did any of you guys find 1 or 3?

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    So, basically i wrote down the torque equilibrium equation where torque equals 0 and the point of reference being the one shown in the diagram. The distance from the point of reference to where Fg is applied is a PLUS b since a is just the distance from the point where F is applied...NOT from the point of reference. The signs you can find using the right-hand rule..i used positive as counterclockwise..so torque is pointing towards you.

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    Anna if u are having trouble with number 3, have a look at Ex5.2 it will help.

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    these are the steps to do number 3. i still have yet to try it though:

    first you need all the euations of the forces

    so horizontal and vertcal

    then you need torque

    so once you hv your torque youll hv lots of L

    you should factor that out

    nd solve for T

    then sub T into the horizontal forcees equation

    nd solve for Rx

    And for Question 2 are we supposed to convert cm to m and when we find b, there's no given units so am i supposed to just multiply it with a and it automatically becomes the same unit as a?

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    the units are given.. it's cm throughout..you don't have to convert because the units for l get canceled out in the end anyways

    i got an answer around 3000 for #3? Anyone else get something similar?

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    yep, it's supposed to be a huge number for #3

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    i got around 4000s. Hey for question 2 is it supposed to be a tremendous number as well. I got like 4450

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    Did anyone figured out #1?

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    No! I've tried multiple ways to do it.. and yet still not getting the right answer. I think I'm messing up my coordiante system and the angles for the forces..

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    Question #1

    T(l1)cos30 + Warm(l2)cos30 - WM(l3)cos30
    solve for T

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    time's up..lol

    Thanks guys!

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