试题与答案

(09年冀州中学期末)水平面上静止放置一质量为M的木箱,箱顶部和底部用细线分别拴

题型:选择题

题目:

(09年冀州中学期末)水平面上静止放置一质量为M的木箱,箱顶部和底部用细线分别拴住质量均为m的小球,两球间有一根处于拉伸状态的轻弹簧,使两根细线均处于拉紧状态,如图所示。现在突然剪断下端的细线,则从剪断细线开始到弹簧恢复原长以前,箱对地面的压力变化情况。下列判断正确的是(       )

A.刚剪断细线瞬间,压力突然变大,以后箱对地面压力逐渐增大

B.刚剪断细线瞬间,压力突然变大,以后箱对地面压力逐渐减小

C.刚剪断细线瞬间,压力突然变小,以后箱对地面压力逐渐减小

D.刚剪断细线瞬间,压力突然变小,以后箱对地面压力逐渐增大

答案:

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