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9-1.Fluid Mechanics
medium
પદાર્થનું વજન હવામાં વજન કરતા પાણીમાં હવામાં વજન કરતાં ત્રીજા ભાગનું છે, તો પદાર્થ ઘનતા ............. $g / cm ^3$
A
$0.5$
B
$1.5$
C
$2.5$
D
$3.5$
Solution
(b)
Given,
Weight of body in water is $\frac{1}{3}$ of total weight in air,
Mean, buoyancy force in water is $\frac{2}{3}$ of total weight in air
Volume of body, $V$
Density of water and body, $\rho_w\ and\, \rho_b$
Apply Archimedes principle
Buoyancy force $=$ weight of water displaces $=\frac{2}{3}$ weight of body in air
$\rho_{ w } Vg =\frac{2}{3} \rho_{ b } Vg$
$\rho_{ b }=1.5 \rho_{ w }$
Density of body is $1.5$ time the density of water.
Standard 11
Physics