I'm having some trouble finding a definitive answer for this problem of my physics lab.(adsbygoogle = window.adsbygoogle || []).push({});

The large quadricep muscles in the upper leg terminate at the lower end in a tendon attached to the upper end of the tibia. The force on the lower leg when the leg is extended are modeled below (attached jpg), where T is the tension in the tendon, w is the force of gravity acting on the lower leg, and F is the weight of the foot. Find T when the tendon is at an angle of 20 degrees with the tibia, assuming that w = 180N, F = 30.0 N, and the leg is extended at an angle of 45.0 degrees with the vertical. Assume that the center of gravity of the lower leg is at its center, and that the tendon attaches to the lower leg at a point one fifth of the way down the leg.

I've been looking through some examples to try to come up with a general idea, but this problem seems somewhat different as no lengths or distances are given except that the tendon attaches 1/5 down the leg. So far, I've found forces in x and y components to get

SUMFx = Tx + wx + Fx = 0

to get Tx = 0.

Then in y direction, I'm not sure if i can do this but i found

Tsin65 - 180 - 30 = 0

to get T = 231.7.

Knowing that this is supposed to be a torque-related problem I also used SUMt = tT + tw + tF = 0. Then tT = rTTsinθ. This is where I am stuck. How would I use the torque equilibrium equation if I am not given any distances? Any hints or suggestions would be really helpful!

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# Homework Help: Equilibrium and Center of Gravity problem

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