Which unit is used to measure work for mechanical power?

The correct unit for measuring work in the context of mechanical power is Horsepower. Horsepower is a unit specifically created to quantify the power, or the rate at which work is done, particularly in engines and motors. It originated in the 18th century as a way to demonstrate the capability of steam engines compared to draft horses.

When thinking about work and power, it's essential to recognize that work is defined as the force applied over a distance, while power is the rate at which that work is done. Horsepower is useful for expressing larger power outputs in practical applications, such as car engines.

Other options, while related to the concept of energy and power, are not specifically used to measure mechanical power in the same way. A Watt is a unit of power that can also measure the conversion of energy but is smaller than horsepower in magnitude. Joules measure energy or work done without directly indicating the time taken, thus not specifically addressing power. Ampere measures electrical current and does not relate to mechanical power directly. Each of these units has its place in physics, but for mechanical power, horsepower is the most appropriate indicator.