7.
The word "horsepower" was first used two hundred years ago. James Watt had made the world's first widely used steam engine. He had no way of telling people exactly how powerful it was, for at that time there were no units for measuring power.
Watt decided to find out how much work one strong horse could do in one minute. He called that unit one horsepower. With this unit he could measure the work his steam engine could do.
He discovered that a horse could lift a 3300-pound weight 10 feet into the air on one minute. His engine could lift a 33-pound weight 100 feet in one minute.
Because his engine did ten times as much work as the horse, Watt called it a ten horsepower engine.
(3)、He made up a unit of measurement based on the strength of a horse.A. 错误
B. 正确
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