题干

如图所示,轻弹簧一端固定,另一端自由伸长时恰好到达O点,将质量为m(视为质点)的物体P与弹簧连接,并将弹簧压缩到A由静止释放物体后,物体将沿水平面运动到B点.若物体与水平面的摩擦力不能忽略,则关于物体运动的下列说法中正确的是(   )

A:A到O速度不断增大,O到B速度不断减小

B:A到O速度先增大后减小,O到B速度不断减小

C:A到O加速度减小,O到B加速度不断增大

D:A到O加速度增大,O到B加速度不断减小

上一题 下一题 0.0难度 选择题 更新时间:2018-02-11 12:01:51

答案(点此获取答案解析)

B

同类题3

阅读理解

    I was a shy girl. I didn't even like to answer the telephone for fear I'd have to talk to somebody I didn't know. I enjoyed the loneliness of exploring nature. However, at school I had to spend all day in the company of others. My escape was reading. I spent a lot of time studying and was rewarded with good grades. My only failure was Spanish—I'd get all. As on my written work and tests, but Ds and Fs on the spoken part.

    Eventually I went to college. During my third year of college, I had enough of being shy and determined to change my outlook and behavior. One day while at school, I noticed an advertisement for positions on the local classical music radio station. I had grown up listening to classical music, and I could easily pronounce names such as Tchaikovsky, Albinoni, and Chopin.

    I had absolutely no background in radio, and absolutely no hope of getting the job. The idea of talking to thousands of listeners in “radio land” terrified me. However, I luckily survived the interview. I was given brief descriptions of symphonies(交响乐)and a public service announcement to read, and a list of composers' names to pronounce. It wasn't hard for me. I left the recording session(录音时段)with a sense of relief and a sense of accomplishment. About two weeks later I actually landed the job. It was a challenging job, but I grew to enjoy it greatly. I began to feel comfortable talking to people.

    Although I now spend many hours each week talking with people, I'm still basically a quiet person. Perhaps it is my soft voice and my quiet nature that helps draw people out as they respond to my questions as I interview them. My former shyness is a fortune, as I can relate to people who feel discomfortable when they talk to newspaper reporters. I still enjoy moments of loneliness and the peace found in nature. But I'm also glad I decided to make a change in my life that has opened many doors and opportunities that I never knew existed.