First slide

Fluid statics

Question

A concrete sphere of radius R has a cavity of a radius r which is packed with sawdust. Specific gravities of concrete and sawdust are respectively 2.4 and 0.3 for this sphere to float with its entire volume submerged under water.Ratio of mass of concrete to mass of sawdust will be :

Easy

A

4
B

2
C

3.2
D

1.8

Solution

For floatation, weight of whole sphere= upthrust
$\frac{4}{3} π (R^{3} - r^{3}) ρ_{1} g + \frac{4}{3} {πr}^{3} ρ_{2} g = \frac{4}{3} {πR}^{3} \times ρ_{w} \times g (R^{3} - r^{3}) ρ_{1} + r^{3} ρ_{2} = R^{3} \Rightarrow \frac{R^{3}}{r^{3}} = \frac{ρ_{1} - ρ_{2}}{ρ_{1} - 1}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App