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 drawing indicates. The forearm weighs 25.0 N and has a center of gravity as indicated. The scale registers 85 N. Determine the magnitude of M.

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 drawing indicates. The forearm weighs 25.0 N and has a center of gravity as indicated. The scale registers 85 N. Determine the magnitude of M.

MathMate · Answer

The forearm weighs 25.0 N and has a center of gravity as indicated.

We do not see the diagram, and there is no description. We do not see what M represents.

In any case, sum moments about the support point of the muscle, at which the reaction is not known. The sum of moments should be zero. Solve for M.