做功总量:W=mgh=300X1000X9.8X20=58800000焦耳=58800千焦耳.所以水泵做功58800千焦耳.
水泵每小时做功:P=W/T=58800/12=4900千焦耳/小时=4900000/3600000=1.36千瓦.