搜题请搜索小程序“爱下问搜题”
问题 问答题

同学们在实验室内测某种小矿石的密度，选用的器材为天平，量筒，小矿石，细线，烧杯和水．

（1）在调节天平横梁平衡时，发现指针位置如图甲所示，此时应将右端的平衡螺母向______调（选填“左”或“右”）．

（2）用调节好的天平称小矿石的质量，放在右盘中的砝码和游码的位置如图乙所示；量筒量出小矿石的体积如图丙所示，由此可知，小矿石的质量为______g，矿石的体积为______cm3，则小矿石的密度ρ=______kg/m3．

答案

（1）由图知，指针向右偏转，所以需将平衡螺母向左调节．

故答案为：左．

（2）小矿石的质量m=50g+10g+2g=62g；小矿石的体积V=80cm3-60cm3=20cm3．

所以小矿石的密度为ρ=

m
V
=
62g
20cm3
=3.1g/cm3=3.1×103kg/m3．

故答案为：3.1×103．

单项选择题

Napoga is a 12-year-old girl in Ghana(加纳), Africa. It is hard for her family to get clean water. Every morning, she leaves home at half past five to get clean water for her family in a village far away. It takes her six hours to get enough clean water for daily cooking and drinking. She has no time to go to school or to play with her friends. Millions of people in the world are like Napoga. They can’t get enough clean water to keep healthy.
Earth Day is April 22. But on all other days, we must also remember it. The water we use is the most important natural resource on the earth.
Water covers 70% of the earth’s surface. But most of that is sea water. We can’t use it for very many things. Fresh water covers only 1% of the earth’s surface.
You probably feel lucky that your life isn’t as hard as Napoga’s. But that doesn’t mean you don’t have to worry about water. We all face serious water problems. One of them is water pollution. All kinds of things from cars, factories, farms and homes make our rivers, lakes, and oceans dirty. Polluted water is very bad for people to drink. And dirty water is bad for fish, too. Now, 34% of all kinds of fish are dying out.
How do cars and factories make our water dirty First, they pollute the air. Then, when it rains, the rain water comes down and makes our drinking water dirty. Dirty rain, called acid rain, is also bad for plants, animals and buildings.
Scientists say that in 30 years, more than half of the people in the world won’t have enough clean water. We have to learn how to save more water for ourselves and our children. Here is some advice for saving water:
· Turn off the water while you brush your teeth. You can save as much as 450 liters each month.
· Leaky taps waste a lot of water. Fix them right away!
· You can easily cut your 10-minute showers in half—and you’ll be just as clean.
· When you wash dishes, don’t let the water run.
· Only wash clothes when you have a lot to wash. If your washing machine isn’t full, you’re wasting water !

On the earth, ______.

A．sea water is widely used than fresh water

B．there is very little water for our living

C．there is 71% of fresh water

D．we don’t need to worry about water
查看答案
单项选择题 A1/A2型题

两侧头痛属于（）

A.厥阴经

B.太阳经

C.阳明经

D.少阳经

E.太阴经
查看答案