This seems like it should be easy but Im not sure what to do. Heres the problem:(adsbygoogle = window.adsbygoogle || []).push({});

The picture to the problem is here: http://www.webassign.net/giancoli/9-65alt.gif

"(a) Calculate the magnitude of the force FM required of the "deltoid" muscle to hold up the outstretched arm shown in Fig. 9-65. The total mass of the arm is 2.8 kg and = 12°.

(b) Calculate the magnitude of the force FJ exerted by the shoulder joint on the upper arm.

I found a) by doing .12 m (sin 12) F - .25 m (2.8 kg) (9.8 m/s^2) = 0. F = 264 N.

But how do I find the force FJ? Confused (we haven't had the lesson on this yet, but trying to get my homework done early because I have a busy week). THANKS for any help!!!

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Equilibrium when applied to muscles and joints! Help, please!

**Physics Forums | Science Articles, Homework Help, Discussion**