Static Equilibrium in Forearm

Question

Hello, I always get stuck every time I try to answer this because of the distance of the dumbbells or the center of mass is not given I cannot continue solving, please help

As a part of his daily workout routine, he lifts 10-kg dumbbells on each hand. His hands

and forearms weigh 4 kg each. If the length of each of his forearms and hands are 0.5 m,

determine the force exerted by his muscles? Assume that the center of gravity of the

forearms are in the middle

Answer 1

Hi Niki D.,

Another poorly framed problem. You can certainly calculate the required torque around his elbow pivot points -- but, (and shame on your instructor!) the distance from the elbow pivot to the point of insertion of the biceps on the radius is missing. This is a third-degree lever, and must be solved as such! P.S. you can look this sort of physiological data up on the web.

-- Cheers, --Mr. d.