Hold your hand out with your elbow at your side and your forearm parallel to the ground. You should notice your bicep muscle flexing in order to keep your forearm in equilibrium in this position, working against the force of gravity. To maintain this equilibrium, how does the force that your bicep exerts on the forearm compare with the force of gravity acting on the forearm?

Explanation:

We shall consider the balance of forearm . The weight is balanced by tension created in the bicep of forearm.

The weight of forearm will act downward . Let it be W. Tension T  of bicep will pull the forearm upwards . Bicep muscle is attached at a point between palm and elbow. Its other end is attached with hind arm . If we hold the forearm parallel to ground , weight acts vertically downwards and tension in bicep makes some angle with the vertical . Let it be θ.

Vertical component of tension T

= T cos θ . It will balance W .

T cos θ = W

T = W / cos θ

the value of cos θ will always be less than 1.

so T > W . or

tension in bicep is more than weight of forearm.

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