Because we can feel that things are very heavy, we think of “weight as being a f

Because we can feel that things are very heavy,we think of “weight” as being a fixed quality, but it is notreally fixed at all. If you could take a one-pound packet of butter 4 000 milesout from the earth, it would weigh only a quarter of a pound.

Why would things weigh only a quarter asmuch as they do at the surface of the earth if we took them 4 000 miles outinto space? The reason is this: all objects have a natural gravity(引力)for all other objects; this is calledgravitational attraction(万有引力). But this power ofattraction between two objects gets weaker as they are farther apart. When thebutter was at the surface of the earth, it was 4 000 miles from the center.When we took the butter 4 000 miles out, it was 8 000 miles from the center,which is twice the distance.

If you double the distance between twoobjects, their gravitational attraction decreases “two times two”. If you make the distance three timesfar away, it gets nine times weaker (three times three). If you make it fourtimes far away, it gets sixteen times weaker (four times four) and so on.

So this is one of the first things weneed to remember: the weight of an object in space is not the same as itsweight on the surface of the earth.

1.Which of the following is right?

A.A thing has the same weight everywherein space.

B.“Weight” is a fixed quality in an object.

C.“Weight” is not a quality in an object.

D.A thing’s weight changes with its placein space.

2.There is    between   .

A. gravity; objects?    B.power;all objects

C.gravity; the two objects only?  D.power;two things

3.A 400 pound man-made satellite is sentto the place 2 000 miles out from the earth. Its weight is about   .

A.200 pounds  B.ahalf pounds

C.100 pounds D.300pounds

4.If we make the distance between objectsfive times as far away,   .

A. it gets twenty-five times weaker

B.their weight gets twenty-five timesweaker

C.their gravity gets twenty-five timesweaker

D.their gravity gets twenty-five timesstronger

5.After reading this passage, we shouldremember that we know the usual weight of a thing   .

A. because it is on the surface of theearth

B.because it is weighed

C.because it is in space

D.because it is not far away from theearth

试题答案

答案：D;A;A;C;A