The figure shows an outstretched arm with a mass (m1) of 4.4 kg. The arm is 56 cm long, and its center of gravity is 21 cm from the shoulder. The hand at the end of the arm holds a 6.0-kg mass (m2). (so its a man holding a dumbell, and his arm is 15 degrees up from the horizontal)
What is the torque about the shoulder due to the weights of the arm and the 6.0-kg mass?
If the arm is held in equilibrium by the deltoid muscle, whose force on the arm acts 5.0 below the horizontal at a point 18 from the shoulder joint what is the force exerted by the muscle?
The Attempt at a Solution
So, I got the first question by determining the force perpendicular to the arm: m2gcos15 and then multiplying that by the distance from the shoulder, .56m. Then I added (m1g)(.21m), the mass of the weight of the arm and the position of its center of mass (.21m)
Now the second question, I am really confused about. I know that I make the deltoid muscle into a tension force, but how do I find out what the tension force is, do I simply do a sum of force in the x and y direction? Or do I have to include torque some how?