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]
A trolley is pushed in a lu y5v5; /pf29yumfae zevel paryvc. h::)k cg-:d6spn h5nt rwking area of a market on a very rainy day. The rht:kdp v:n n -:h.grsc)6cw5yain fills the trolley at a rate of $R\,kgs^{−1}$. Ignoring frictional forces, what is the force needed to move the trolley at a constant speed of v?
A. $Rv$
B. $\frac{R}{v}$
C. $\frac{v}{R}$
D. $R+v$
参考答案: A
本题详细解析:
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