问题 选择题

物体受在同一直线上两个力的作用,大小分别是30N和50N,这两个力的合力大小可能是(  )

A.50N

B.40N

C.30N

D.20N

答案

作用在一个物体上的两个力,F1=30N、F2=50N,

当两个力的方向相反时,其合力最小:F=F2-F1=50N-30N=20N,

当两个力的方向相同时,其合力最大:F=F1+F2=30N+50N=80N,

因为两个力的方向不确定,所以其合力的大小可能等于20N,也可能等于80N,由上述可知,选项A、B、C不正确.

故选D.

阅读理解

Bend over, take a deep breath and drink some water! This is just one of the hundreds of tips you might get if you have the hiccups(打嗝). Hiccups are so mysterious. We really don’t know why they start and why they stop.

Everyone has a favorite cure for a case of the hiccups. Some people think that a good scare is necessary to get well. Others eat a teaspoon of sugar. Still others drink a glass of water with a knife in it.

An American man named Jack O’Leary claimed to have hiccupped 160 million times over a period of eight years. He tried 60,000 cures, but none of them worked. Finally he prayed to Saint Jude, the saint of Hopeless cases, and his hiccupping stopped immediately.

It took a British plumber eight months to cure his hiccups. People from all over the world wrote him letters with suggestions for getting well. He tried them all, but the hiccups continued. Finally, he drank a “secret’’mixture someone had sent him. By that evening his hiccups were gone. Why did these cures work for these two men? No one really knows. But people who have studied many cases of hiccups have an idea. Hiccups usually go away if you believe in the cure.

小题1:

________might be the best cure for hiccups.

A.Special pills

B.A spoonful of salt

C.Cold water

D.What you believe in小题2:

The plumber spent________in stopping his hiccups.

A.4 hours

B.2 days

C.8 months

D.8 years小题3:

According to the passage, which of the following is TRUE?

A.We know why the hiccups start, but we don’t know how to stop them.

B.Saint Jude is an expert in curing the hiccups.

C.The British plumber drank a secret mixture given by an experienced doctor and then became well.

D.Some people think that a good scare is a cure for a case of hiccups.小题4:

What is the main idea of this passage?

A.Different ways to stop hiccups

B.What makes hiccups happen

C.How to get hiccups

D.Jack O’Leary’s hiccups

单项选择题