Question

小明的爸爸新买了一辆小汽车,小明坐者这辆汽车均速行驶14km用时2h消耗汽油9kg其发动机率为23kW则

Answer 1

(1)v=s/t=14km/2h=7km/h=1.94m/s

F=P/v=23kW/1.94m/s=11.83k N

(2)Q=mq=9kg*46MJ／kg=414MJ

汽车做的功=Pt=23kW*2h=46kWh=165.6MJ

效率=汽车做的功/Q=165.6MJ/414MJ=40%