Question

Why are the forces exerted on the outside world by the limbs of our bodies usually much smaller than the forces exerted by muscles inside the body?

Short answer

The limbs in the human body are the third-class lever.

Step-by-step solution

Force

A force is an external factor that can change the rest or motion of a body. It has a size and a general direction.

Explanation

The mechanical advantage of a machine is,

$$\begin{gathered} MA=\frac{F_{\circ }}{F_i} \\ =\frac{l_i}{l_{\circ }} \end{gathered}$$

For,$l_i<I_{\circ }$, $F_i>F_{\circ }$.

The elbow serves as the fulcrum if a load is on the palm. The effort is applied by flexing the biceps. The force exerted by the muscles is the input force, and the force applied by the limbs on the outside world is the output force. As ,$l_i<I_{\circ }$ the input force is always more significant than the output force. The human limbs are the third-class lever.