题目

  36   One of the best things you can possibly do is to start your own club. It’s great fun especially if you are the sort of person who feels there’s never anything to do during the school holidays. The first thing you need to come up with is an idea for your club.   37   Pets, clothes, pop music or dancing groups, sports, making things? The list is endless. Next you need some friends to be in your club with you.   38   All you need is three or four other people who are interested in the same thing as you.   39   You should all sit down somewhere together with lots20．如图1所示，质量为1kg的滑块（可视为质点）在离地面高h=2m的A点沿粗糙弧形轨道以初速度v0=4m/s开始下滑，到B点的速度为6m/s，通过粗糙水平轨道BC后，再沿着光滑的半圆轨道运动．已知滑块与水平轨道BC间的动摩擦因数μ=0.10，且C、O、D三点在同一竖直线上，设水平轨道长BC=x，光滑半圆轨道的半径大小为0.4m，g=10m/s2．（1）滑块从A到达B克服摩擦做的功；（2）若x=2m，则滑块刚过C点时对圆轨道的压力是多大？（3）在图2坐标系内画出滑块过D点对圆轨道的压力FD与水平轨道长x之间关系图象．