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Question:

If M is the mass of water that rises in a capillary tube of radius r, then mass of water which will rise in a capillary tube of radius 2r is:

M

2M

4M

M2

Solution:

Correct option is C. 2M
Height of liquid rise in capillary tube
h=2Tcosθ/ρrg ⇒h ∝ 1/r
when radius becomes double height become half
∴h'=h/2
Now ,M=πr²h × ρ
M'=π(2r)²(h/2) × ρ=2M