如图甲所示，把纸带固定在质量为50g的钩码上，让纸带穿过正确安_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题多选题

如图甲所示，把纸带固定在质量为50g的钩码上，让纸带穿过正确安装的打点计时器，接通电源，然后松开纸带，让钩码自由下落，计时器在纸带上打下一系列的点，得到如图乙所示的纸带．用刻度尺测量起始点O（钩码刚要下落时，打点计时器在纸带上打下的点）到各点的距离，并知道交流电源的频率是50Hz，根据上述数据，在此实验中可以做到（　　）

A．测出当地重力加速度的精确值

B．计算出计时器在纸带上打D点时钩码的动能

C．计算出钩码下落过程中受到的合外力大小

D．较准确地验证机械能守恒定律

答案

BCD

完形填空

I was feeling a little blue because my mother had been laid off from her job and she had lots of bills to pay. It left me wondering what was going to happen to us now.
I got off the college shuttle bus and started walking. That’s 36 I heard piano music and singing rising above the noise of the people and the traffic. I walked a little slower so that I could 37   where it was coming from. 38   the crowd I saw a young lady sitting at a piano with a carriage next to her. She was singing songs about love, keeping on trying, and not underestimating (低估) the power within yourself. The way she was singing    39   me a bit. I stood there watching her play for about fifteen minutes, thinking that it must      40   to perform alone in the middle of a crowded place.
She must have felt my 41   because she would 42 look in my direction. Then I walked over and put some 43     in her carriage and she said, “Thank you”. Instead of continuing my way home, I said to her, “I have been 44     a rough time lately, but you’ve made me 45 again.”
“I’m happy that I could help,” she replied. “Why are you so sad?”
“Well, my mum told me she had got    46   from her job, and that made me sad. I’m not so sure what to do …”
“You see, here’s the problem,” she explained. “While you were        47   , your head was down. Don’t look 48 , because 49   comes in different ways and if your head were down, you might lose it.”
She also explained to me that she saw a lot of 50 people in the world and she tried to bring more 51 by sharing motivational (鼓舞人心的) music. She told me that when she wasn’t making music she studied 52  . So, that was how she knew some of the things she was telling me.
I 53     a little wider because I knew that she was doing a good thing. So, after we 54, my heart was 55      and lightened by a musical soul!

C．take action

D．take courage

B．performance

B．occasionally

A．going through

C．taking over

D．running towards

A．opportunity

D．indifference

问答题

试述腮腺混合瘤的临床表现、治疗原则及其恶变的特征。（10分）