# 有少少問題?

Two trains move towards each other.Each train is going 100 kiometres per hour(kph).How fast do they pass each other?

a.50 kph

b.100kph

c.200kph

d.None of the above

The speed of light is about 300000kilometres per second.If you travelled close to the speed of light and your twin stayed on Earth,what would happen?

a.You would get heavier

b.You would age slower than yourtwin

c.You would shrink

d.all of the obove

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• 1 decade ago

1. The two trains are moving with 100 kmh-1 (kph), they are moving in opposite velocity.

So, making use of the concept of relative velocity to solve this problem.

So, the required answer = 100 + 100

= 200 kph

So, the answer is C.

(Note that when dealing with the questions that the objects are moving in high velocity, which is proximity to the speed of light, you cannot use relative velocity to do the question.)

2. The answer is D.

You will grow slower than that of your twins on the Earth. This is due to time expansion.

Since you are moving with high velocity, which is comparable to that of the speed of light, according to Relativity, you will experience a time expansion on the spacecraft. However, you don’t even notice the change. This seems to violate your intuition, but it is true. When you are travelling in light speed, the time will expanded infinity, and the time in the spacecraft suspended…

By speed of light is a constant, the time expanded, the distance should be shortened. So, you will shrink. Yes, if you are travelling in light speed, you will disappear… You will have no dimension at all…

By Relativity, your mass will increase with speed when it is comparable to that of light. When you are travelling in light speed, you mass will be infinity large…

Relativity proposed by Einstein is a real breakthrough in Physics. With this brand new theory, the sophisticated and authoritative classic Newton’s mechanics seems to collapse. But don’t worry, in real life, where objects are moving in quite a low speed (compare to that of light), Newton’s law of motion is still a good approximation.

For further details, please go to the following website. I have answered a similar question before.

http://hk.knowledge.yahoo.com/question/?qid=700707...

Source(s): Myself~~~