A small spherical ball of radius 0.1 mm and density 104 kg m$-$3 falls freely under gravity through a distance h before entering a tank of water. If, after entering the water the velocity of ball does not change and it continue to fall with same constant velocity inside water, then the value of h will be ___________ m.
(Given g = 10 ms$-$2, viscosity of water = 1.0 $\times$ 10$-$5 N-sm$-$2).
Answer (integer)
20
Solution
<p>$\sqrt {2gh}$ = terminal speed</p>
<p>$\Rightarrow \sqrt {2gh} = {2 \over 9}{{{r^2}g(\rho - \rho ')} \over \eta }$</p>
<p>$$ = {2 \over 9} \times {{{{10}^{ - 8}} \times 10 \times 9000} \over {{{10}^{ - 5}}}}$$</p>
<p>$\Rightarrow h = {{400} \over {2g}}$</p>
<p>$\Rightarrow h = 20$ m</p>
About this question
Subject: Physics · Chapter: Properties of Solids and Liquids · Topic: Elasticity
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