An athlete at the gym holds a 3.0 kg steel ball in his hand. His arm is 62 cm long and has a mass of 3.8 kg, with the center of mass at 40% of the arm length from the shoulder.

Question

What is the magnitude of the torque about his shoulder due to the weight of the ball and his arm if he holds his arm straight out to his side, parallel to the floor?

What is the magnitude of the torque about his shoulder due to the weight of the ball and his arm if he holds his arm straight, but 45∘ below horizontal?

Answer 1

1st part ... forces are m*g , distances are given

2nd part ... same forces ... distances are reduced by geometry
... distances equal to 1st part multiplied by sin(45º)