题干

弹性介质中波源O沿竖直方向振动产生的简谐横波以速度v=20m/s传播,M、N为与O在同一直线上的两质点.它们到O的距离分别为OM=24m、ON=12m.波源O振动1.2s后在直线MN上形成的波形如图所示,不计波传播过程中的能量损失.下列说法正确的是(   )

A:波源的振动周期为0.4s

B:波源开始振动的方向向上

C:波传播到N时,N先向下振动

D:M与N的速度方向始终相同

E:M与N的加速度大小始终相等     

上一题 下一题 0.0难度 选择题 更新时间:2018-12-19 08:17:39

答案(点此获取答案解析)

A,C,E

同类题2

阅读理解

       Oxford University has introduced confidence classes for female students to get them to compete for jobs in future and win chances to work in best companies.

       They may be young and gifted, but research at the excellent institution has found that female undergraduates(大学生)are shying away from applying for jobs in banking, finance, management consultancy(咨询), engineering and resource management. Partly as a result, starting salaries for women when they graduate are on average £2,000 to £3,000 lower than their male counterparts.

    “Women are earning less on leaving Oxford.It is ridiculous,”said Jonathan Black, the careers service director at the university.“We have high quality and high achieving students of both genders.But it appears that women are selecting lower paid jobs. They accept more prejudice in certain industries and are saying 'I won't struggle for that really high paid job'. We are not trying to push loads of women but we are trying to say, you should feel able to apply for these sorts of jobs.Boys seem to have more self­confidence and see the bigger picture generally, even though their self­belief is not necessarily based on any greater academic advantage.”

       The four­day programme at Oxford will help 45 female undergraduates improve their self­confidence and decision­making, think positively and build up their strengths. Confidence training will teach them how to deal with the opposition and challenging situations.

       Successful female employees from RBS and BP, which are supporting the course, will talk about their lives and careers. RBS's involvement follows a promise by the bank to increase its national percentage of female graduate applications from 35 percent to 50 percent by 2014.

       Sophie Kelley, 20, studying law at Oxford, is hoping the course will make her more confident in courses and interviews.“I am applying to London's law firms for vacation schemes and it is so competitive,”she said.“The rejection letters don't give any real feedback(反馈), so I'm expecting the programme might give me a hand and some advice.”

Notes

①institution n.社会公共机构,制度,制定 ②counterpart n.与对方地位、作用相当的人(或物) ③gender n.性别 ④prejudice n.偏见,成见