1.Calculate the net torque (magnitude and direction) on the beam in Figure P8.3

Question

1.Calculate the net torque (magnitude and direction) on the beam in Figure P8.3 about the following axes.

(a) an axis through O, perpendicular to the page
     N

Calculate the net torque (magnitude and direction) on the beam in Figure P8.3 about the following axes. an axis through O, perpendicular to the page N m an axis through C, perpendicular to the page N m The arm in Figure P8.7 weighs 42.0 N. The force of gravity acting on the arm acts through point A. Determine the magnitudes of the tension force vector F rightarrow t in the deltoid muscle and the force vector F rightarrow s of the shoulder on the humerus (upper-arm bone) to hold the arm in the position shown.

Explanation / Answer

1)
a) Tnet = 2*25*sin(60) -4*10*sin(20)

        = 29.62 N.m

b)
Tnet = 2*30*sin(45) - 2*10*sin(20)

    
2)

net torque about the point O should be equal to zero.

Tnet = Ft*0.08*sin(12) - Fg*0.29 = 0


Ft = Fg*0.29/(0.08*sin(12)

   = 732.28 N

net force in y-direction should be = 0


Ft*sin(12) - Fg - Fsy = 0

Fsy = Ft*sin(12) + Fg
Fsy = 194.25
netforce in x-direction should be equal to zero.
Fsx - Ft*cos(12) = 0
Fsx = Ft*sin(12) = 716.28 N
Fs = sqrt(Fsx^2+Fsy^2) = 742.15 N

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