Which physical concept describes how machines can amplify force?

The correct concept that describes how machines can amplify force is mechanical advantage. This principle refers to the ratio of the output force produced by a machine to the input force applied to it. Essentially, mechanical advantage allows a machine to provide greater force than what is physically applied, making tasks easier to perform.

For instance, using a lever, by placing the fulcrum closer to the load, one can lift a heavy weight with a much smaller input force. This amplification of force is what characterizes mechanical advantage, a fundamental concept in understanding how simple machines operate.

In contrast, mechanical efficiency relates to how well a machine converts input energy into useful work and does not directly assess force amplification. Work input refers to the energy put into a machine, while energy transfer deals with how energy moves from one system to another. Neither of these concepts specifically outlines the relationship between input and output forces as mechanical advantage does.