本题目来源于试卷: Physics Bowl by Topic 4: Kinematics - part III Projectile Motion，类别为 美国物理杯赛(Physics Bowl)
[单选题]
02.41: A person throws a small object from the top of a buil hj; ;aky1sma*ding at an angle of j ;m*s;a yk1ha*b +c1okf v+xd02 swhb8lobw5ow2b b++w1f0k l v8cbsxh5*od$30^{\circ}$ above the horizontal. At the instant that the object returns to the same height from which it was thrown, at what rate is the speed of the object changing? Ignore air resistance and let g be the acceleration due to gravity.
A. 0
B. $g \tan{30^{\circ}}$
C. $g \sin{30^{\circ}}$
D. $g \cos{30^{\circ}}$
E. $g$
参考答案: C
本题详细解析:
暂无
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