Don Nightingale, age 13, of St. Catharines, Ont., for his question:

 What is a horsepower?

A horsepower is a measure of work done in a certain time. We use it to estimate the amount of work an engine can do. A force of one horsepower can lift 550 pounds one foot straight up in one second.

Of course, all engines are not built for lifting. There is pushing, pulling and turning work to be done. But the amount of work needed to lift a certain weight in a certain time can be estimated with accuracy. This gives us the horsepower unit. It is then used to estimate the work of pushing, pulling or turning of which a machine is capable.

The horsepower unit of work was named out of sympathy for the hard working horse. James Watt designed a steam engine which he hoped would relieve the burden of the mine horses. He estimated the work his engine could do in terms of the work done by the horses. Actually, no horse could do work equal to one horsepower. Three horsepower are about equal to the work which four strong horses can do.