Your elbow acts as a pivot for your forearm Imagine you hold

Your elbow acts as a pivot for your forearm. Imagine you hold a dumbbell (weight = 130.N) which is a distance of 0.360 m from the pivot point. Your bicep is attached as shown below, a distance of 0.028 m from the pivot point. Find the upwards force of the bicep to keep this in static equilibrium, as well as the x and y forces of the elbow. If the maximum force the bicep can exert is 3400 N, what is the maximum weight of a dumbbell that can be held in this manner?

Solution

6.a) balancing moment about pivot point,

(0.028 x Fbicep) - (0.360 x mg) = 0

0.028Fbicep = 0.360 x 130

Fbicep = 1671.43 N

b) now Fbiceps = 3400 N

so (0.028 x 3400) - (0.360 x W) = 0

W = 264.44 N