本题目来源于试卷: Newton’s law of motion，类别为 美国物理杯赛(Physics Bowl)
[单选题]
06.15: A crate of toys remain*e+b;l fzxhw8cl: 1nu s at rest on a sleigh ahsb) /yhblj;+s the sleigh is pulled up a hill with an incre;hjy)sb+/h l basing speed. The crate is not fastened down to the sleigh. What force is responsible for the crate’s increase in speedup the hill?
A. the contact force (normal force) of the ground on the sleigh
B. the force of static friction of the sleigh on the crate
C. the contact force (normal force) of the sleigh on the crate
D. the gravitational force acting on the sleigh
E. no force is needed
参考答案: B
本题详细解析:
暂无
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