本题目来源于试卷: 美国2021年物理杯赛真题 PHYSICS BOWL 2021，类别为 美国物理杯赛(Physics Bowl)
[单选题]
A force, $F$, could be applied to a cart in a variety of directions as shown at right. Which of the applications of $F$ would result in no work being done?
A. A
B. B
C. C
D. D
E. All of them result in work being done.
参考答案: C
本题详细解析:
The work done by a force is given by $W = \vec F \times \vec d = Fd cos \theta$. If the direction of the force $F$ is perpendicular to the direction of the displacement $d$, the angle $\theta$ equals $90^\circ$ which means $cos \theta$ equals 0 so that the work done by the force is zero or there is no work being done.
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