问题 应用设计题

请画出右上图中物块A对斜面的压力及A受到的重力。

答案

考点:

分析:重力是物体受到的力,物体的重心在物体的几何中心,重力的方向总是竖直向下的,过物体的重心表示出重力的方向即可;

压力是接触面受到的力,因此压力的作用点在接触面上,即物体与接触面的中点;然后根据压力的方向垂直于受力面,并过压力作用点表示出压力的方向即可.

解答:解:过物体重心画带箭头的线段,方向竖直向下,用符号G表示;

在斜面上选取物体与接触面的中点为压力的作用点,过压力作用点画垂直于斜面、带箭头的线段,用符号F表示.

如图所示:

点评:本题的关键是确定压力和重力的作用点和方向,并会用力的图示表示力的三要素.注意物体对斜面的压力要小于物体所受重力.

听力题

阅读下面短文,用括号内所给动词的适当形式填空(必要时可加情态动词或助动词)。

" Everything happens for the best," my grandmother said whenever things weren't going my way. "Don't worry, one day your luck小题1:_______(change). "

Grandmother was right, as I discovered after graduating from college. I had decided to be sports announcer (广播员) in a radio station, so I 小题2:_______ ( go) to Shanghai and knocked on the door of every station. But I got refused every time.

In one station, a kind lady said my problem was short of experience. " Get some work with a small station and小题3:______(work) your way up ," she said.

I couldn't get a job there, either. Then my dad told me a businessman had opened a company and needed someone小题4:_______ ( manage) the sports center. But again, I didn't get the job.

I felt really down. "Your luck will change," Granny reminded me. I tried another radio station in Beijing. But the owner, a nice man, told me he already had someone.

As I left his office, I asked, " How can someone be a sports announcer if he 小题5:_______(not, get) a job in a radio station?"

I 小题6:_______( wait) for the elevator when I heard the man call, " What was that you said about sports? Do you know anything about football?" I 小题7:_______(put) in front of a microphone and asked to imagine I was commenting (评论) on a football game. "Now you 小题8:_______ (watch) the football game between Lu Neng and Shen Hua. . . "

On my way home, Granny's words came back to me, " One day your luck will change, boy. And when it 小题9: _______( happen) , it'll feel twice as good because of all the disappointment (失望) you 小题10: _______ ( have) . " At that moment I knew just what she meant.

单项选择题