问题 多选题

如图所示,一水平轻质弹簧一团固定在竖直墙上,一端系一小球,小球与水平地面的摩擦.将小球从弹簧原长O位置拉至A处由静止开始释放,小球向左运动到B处速度恰好为0,此过程中,下列说法正确的是(  )

A.小球在O处的加速度不为零

B.小球在O处的加速度为零

C.小球达到最大速度的位置在AO之间

D.小球达到最大速度的位置在OB之间

答案

A、小球经过O点时,弹簧的弹力为零,则小球的合力F=f,知加速度不为零.故A正确,B错误.

C、从A到O的过程中,当小球所受的弹力和摩擦力相等时,速度最大,知小球最大速度的位置在A0之间.故C正确,D错误.

故选:AC

阅读理解

Nowadays, millions of lonely singles are now going online instead. The World Wide Web is quickly becoming the world’s most popular matchmaker(媒人).

Singles are flocking(涌向)to the Internet mainly because their busy lifestyles leave them little time to look for a significant other. Using dating sites(约会网址)is quick and convenient. Many singles say the regular dating scene has just led them from one bad experience to another and are ready to try something else. Dating sites also make it easy to avoid someone you are not interested in. In the real world, however, ignoring someone you don’t like can be difficult.

Despite all the advantages, online dating also presents its own set of problems. People aren’t always those who they declare to be in their online description. Safety is another concern. You are just likely to find a criminal online as you are Mr. or Miss Right.

Online dating experts recommend following a few safety tips:

Guard your personal information. Never give out your personal information online. This includes your last name, phone number, home address and place of work.

Watch for red flags. Do any of the people you are chatting with make disrespectful comments? Do they try to control you? Do they give false information about themselves? If so, forget them!

Meet in a safe place. When meeting someone in person, choose a public location with other people around.

Following these tips and you might be able to find the person of your dreams.

小题1:According to the passage, many lonely singles don’t appreciate the regular dating scene because it is _____________.

A.unpopular

B.troublesome

C.convenient

D.forgettable小题2:The underlined words in the second paragraph “a significant other” means _______”.

A.a true friend

B.a matchmaker

C.a marriage partner

D.a happy family小题3:Which of the following is NOT a suitable place for meeting someone you get to know through the Internet for the first time?

A.At his / her house.

B.At the museum.

C.At McDonald’s.

D.At the bookstore.小题4:From this passage, we can infer that ____________.

A.there are mostly homely and unemployed people online

B.the police had better find criminals online

C.we can find love only through the dating sites

D.following safety tips ensures a safe online dating experience

填空题