Question

Water rises upto a height \(h\) in a capillary tube on the surface of the earth. The value of \(h\) increases, if the capillary tube apparatus is kept

• A. in a lift going upward with acceleration
• B. on the sun
• C. on the poles
• D. in a lift going downward with acceleration \(a\) where \(a

Hint:

Capillary rise is inversely proportional to effective gravity.

Answer 1

The Correct Option is D

Step 1: Expression for capillary rise.
Capillary rise is given by \[ h = \frac{2T\cos\theta}{\rho g r} \]

Step 2: Effect of acceleration on effective gravity.
In a lift moving downward with acceleration \(a\), effective gravity becomes \[ g_{\text{eff}} = g-a \]

Step 3: Effect on height of capillary rise.
\[ h \propto \frac{1}{g_{\text{eff}}} \] When \(g_{\text{eff}}\) decreases, \(h\) increases.