题目

There was a proud teak(柚木) tree in the forest. He was tall and strong. There 【1】 (be) a small herb（香草）next to the tree.The teak tree said, I am very handsome and strong. No one can defeat me.”When 【2】 (hear) this, the herb replied, Dear friend, too much pride is bad.Even the strong will fall one day.The teak ignored (忽视)the herb’s words. He continued to praise 【3】 (he).A strong wind blew. The teak stood 【4】 (brave).Even when it rained, the teak stood strong by spreading its 【5】 (leaf). During these times, 【6】 herb bowed(弯曲) low. The teak made fun如图所示,在倾角为θ的粗糙斜面上,有一个质量为m的物体被水平力F推着静止于斜面上,已知物体与斜面间的动摩擦因数为μ,且μ<tanθ, 最大静摩擦力等于滑动摩擦力 （1）若物体恰好不下滑,则推力F为多少?（2）若物体恰好不上滑,则推力F为多少?