Mike Stevens, age 12, of Visalia, Calif., for his question:

WHAT IS HORSEPOWER?

Horsepower is a unit used to express an engine's rate of doing work. The term was first used by a Scottish engineer named James Watt. He used it to compare the power of steam engines to the power of horses.

Today the horsepower term is used to express an engine's power. One horsepower is defined as 550 foot¬pounds of work per second, or 33,000 foot pounds of work per minute. One foot pound is the work needed to lift one pound one foot.

The metric unit of power is the watt. One horsepower equals 745.7 watts.

According the Society of Automotive Engineers' rating, horsepower is computed by squaring the diameter of an engine's cylinders and dividing by 2.5.