If an object weighed one pound on the surface of the earth, how much would it we

游客2024-10-12  7

问题 If an object weighed one pound on the surface of the earth, how much would it weigh 4,000 miles above the earth? [br]  
Because we can feel that things are heavy, we think of weight as being a fixed quality in an object, but it is not really fixed at all. [18]If you could take a one pound packet of butter 4,000 miles out from the earth, it would weigh only a quarter of a pound. Why would things weigh only a quarter as much as they do at the surface of the earth if we took them 4,000 miles out into space? [19]The reason is this: All objects have a natural attraction for all other objects; this is called gravitational attraction, but this power of attraction between two objects gets weaker as they get farther apart. When the butter was at the surface of the earth, [20]it was 4,000 miles from the centre, in other words the radius of the earth is 4,000 miles. When we took the butter 4,000 miles out, it was 8,000 miles from the centre, which is twice the distance. If you double the distance between two objects, their gravitational attraction decreases four times weaker. If you treble the distance, it gets nine times weaker. If you take it four times as far away, it gets sixteen times weaker and so on.

选项 A、2,000.
B、4, 000.
C、8,000.
D、16,000.

答案 C

解析 短文中提到,地球的表面离中心4000英里,也就是半径为4000英里,由此可知直径为8000英里。
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