Question

In an isometric exercise a person places a hand on a scale and pushes vertically downward, keeping the forearm horizontal. This is possible because the triceps muscle applies an upward force perpendicular to the arm, as the figure indicates. The forearm weighs 19.1 N and has a center of gravity as indicated. The scale registers 115 N. Determine the magnitude of M.

Answer 1

M is 0.025 m from the balance point. So 0.025*M is one torque.
The distance from the center of gravity is 0.15m so the weight of the for arm is 23N*0.15 m which makes a second torque. Both of these go clockwise.
The third torque is the reading on the scale and it goes counterclockwise (It holds the other two in balance since the other two go clockwise. 0.3*88N

0.025M +23*0.15 = 0.3*88
0.025M + 3.45 = 26.4
0.025M = 22.95
M = 918 N

This person is very strong, or I think so. The amount of effort put into the pressure is the equivalent of lifting something that is 93.58 kg