Final answer:
Leverage is a mechanical principle exemplified by the use of a lever which operates on the principle of moments and follows the second condition of equilibrium, crucial for the function of simple machines and understanding the human body's mechanics.
Step-by-step explanation:
One mechanical principle as it applies to a specific activity is leverage. In physical mechanics, leverage refers to the advantage gained by using a lever. Levers operate on the principle of moments, where the torque produced by a force applied at one end of the lever is counteracted by a force at the other end. According to the second condition of equilibrium, the torque entering a machine must be equivalent to the torque leaving it. This holds true for simple machines like levers, where the mechanical advantage is the ratio of output force to input force.
In the human body, statics is crucial for understanding strains on muscles and bones. Many lever systems in the body have a mechanical advantage significantly less than one. When designing an investigation to measure the mechanical advantage and efficiency of simple machines such as a lever, one would use tools like a spring scale and a tape measure to assess these values accurately.