Thursday, August 14, 2008

Interesting question

In Pole to Pole, an early science fiction story by George Gtiffith, three explorers attempt to travel by capsule through a naturally formed tunnel directly from the South Pole to the North Pole. According to the story, as the capsule approaches Earth’s centre, the gravitational force on the explorers becomes alarmingly large and then, exactly at the centre, it suddenly but only momentarily disappears. Then the capsule travels through the second half of the tunnel, to the North pole.
Check Griffith’s description by finding the gravitational force on the capsule of mass m when it reaches a distance r from Earth’s centre. Assume that Earth is a sphere of uniform density p.

This is a question I saw from a physics book. If you work it out, you can find the interesting part.
Hint: use Newtonian Gravitation law. F=G(Mm)/r^2. Remember Newton’s shell theorem: a uniform shell of matter exerts no net gravitational force on a particle located inside it.

I will show the answer SOON! ^.^

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