In an artificial satellite, a space traveler tries to fill a pen by dipping it in ink. The amount of ink filled in the pen as compared to the amount of ink filled on the Earth's surface will be:

A) less

B) more

C) same

D) nil

The answer is B) more but I can't understand why?
Is it because the acceleration due to gravity, $g$, is less there, so the ink rises faster?

  • $\begingroup$ What is the mechanism by which the pen is filled? Capillary action? $\endgroup$ – Brandon Enright Dec 7 '13 at 5:10
  • $\begingroup$ Nothing is said about it in the question. But yes, I think it is capillary action. $\endgroup$ – Ris97 Dec 7 '13 at 5:12

A space traveler on an artificial satellite will be in freefall around the planet it is orbiting. So the ink will not experience any acceleration relative to the pen due to the planets gravity.

On earth the ink gets sucked up by the pen due to capillary action, but is counteracted by gravity. While in orbit the full "force" of capillary action can be used to suck up ink into the pen.

A nice demonstration of this is a special designed coffee cup onboard of the ISS.

  • $\begingroup$ So, it is because of reduced $g$ or gravity up there, right? $\endgroup$ – Ris97 Dec 7 '13 at 5:50
  • $\begingroup$ No, if there was on atmosphere on earth to slow you down, you would be able to orbit earth just above the surface (assuming you will not hit an mountain). When in orbit you move around the the body faster than you will fall towards it, which makes you fall around it. $\endgroup$ – fibonatic Dec 7 '13 at 5:59
  • $\begingroup$ @Ris97 $g$ isn't really reduced but because orbiting objects are in free-fall the acceleration isn't felt as a force $\endgroup$ – Brandon Enright Dec 7 '13 at 6:03

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