A long capillary tube is inserted in water vertically. Water rises to a certain length of the tube. If we want to increase the length for which water will rise, we can
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Water rises in a capillary tube due to surface tension and the adhesive force between water and the glass wall. The height is given by Jurin's law: , where is surface tension, is the contact angle, is density, is gravity, and is the tube radius. To increase , we must decrease the effective gravity. Placing the apparatus in a downward-accelerating elevator reduces the net downward acceleration, thus increasing the height.
Final answer: Place the whole apparatus in an elevator accelerating downwards.