本题目来源于试卷: Space Time & Motion A.2 Forces & Momentum，类别为 IB物理学
[单选题]
An electric motor is used to raise a block of mass 18.0 kg vexg 8gxxxi3j: le7,uc8rz gs4y k;; -amrti8x1 +cbl(qx:hj3dr t+g hc0x ccally to the top of a building at a coh3(cxt xchxcl81grj:d ++ 0bqnstant speed of $1.5\,ms^{−1}$. If the power rating of the motor is 297 W, calculate the efficiency of the motor.
A. 9%
B. 75%
C. 61%
D. 91%
参考答案: D
本题详细解析:
| 
