Water, dripping at a constant rate from a faucet, falls to the ground. At any instant there are many drops in the air between the faucet and the ground. Where does the center of mass of the drops lie relative to the halfway point between the faucet and the ground? (a) Above it (b) Below it (c) Exactly at the halfway point

When I looked at this, I thought the answer is (b) below it since if the water drop and the ground are in a system, then the center of mass will be nearer to the heavier object, which is the ground. But when I looked up the answer it was (a) above it. Could you please explain why? Thank you!


Consider just a single water drop. During its accelerated motion downward (its decent), does it spend more of its time above the halfway point, below the halfway point, or does it spend an equal amount of time in each?

Answering that question may help you.

  • $\begingroup$ I see.. But does it only apply to constant rate of dripping? If the dripping rate is increasing/decreasing will the solution be different? P.S: Thanks for the edit! $\endgroup$ – archipelagoS Jun 29 '14 at 4:34
  • $\begingroup$ rate is surely independent of the fact @BMS is talking about, rate relates multiple drops but gravity determines speed and position of a single drop $\endgroup$ – RE60K Jun 29 '14 at 10:17
  • $\begingroup$ At any given time the center of mass could be anywhere. The result above is valid for time averages. $\endgroup$ – BMS Jun 29 '14 at 15:35

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