题干

一质点做简谐运动,则下列说法中正确的是(   )

A:若位移为负值,则速度一定为正值,加速度也一定为正值

B:质点通过平衡位置时,速度为零,加速度最大

C:质点每次通过平衡位置时,加速度不一定相同,速度也不一定相同

D:质点每次通过同一位置时,其速度不一定相同,但加速度一定相同

上一题 下一题 0.0难度 选择题 更新时间:2019-06-24 04:07:57

答案(点此获取答案解析)

D

同类题3

根据短文理解,完成下列各题。

      Before the spring Festival, which is the most important festival in China, millions of passengers are struggling to make the once-a-year trip home. Because of a power failure caused by snow, more than 136 trains were forced to stay in Hunan Province. Almost 150,000 passengers were stopped from going back their homes. It's reported that the losses will be 111.1 billion yuan.  

In central China's Hunan Province, one of the worst hit area, seven people have died and snow is affecting(影响) the lives of 25.22 million people in 14 cities and 112 counties across the province. Though the power supply resumed(恢复) at 4:00 p.m. Saturday, 50 trains remain stranded (滞留) between Hengyang City in Hunan and Guangzhou provinces. And in Guangzhou, an official with Guangzhou railway authorities said the number of stranded passengers in Guangzhou City alone could hit 600,000 on Monday if the situation continued.

How to solve the problems as soon as possible? In order to help the passengers meet their families and solve the traffic problems, our government do what they can. First, The Ministry of Railways Ordered 63 trains to go to Guangzhou via (通过) the Beijing-Kowloon Railway Line or Shanghai-Kunming Railway Line instead of the Beijing-Guangzhou Railway Line. Second, the ministry also organized 35 trains from Beijing, Wuhan and Nanchang cities to help transport the stranded passengers. The thirdly, Guangdong authorities sent 15 million text messages (短信)warning drivers not to take highways leading north. Some Guangzhou citizens try their best to help the stranded passengers, such as offering medicine, raising money and cooking free meals for the stranded students.

      The snow disaster(雪灾) is so terrible, but all of the Chinese and government is trying their best to succeed in beating it.