A boy has $60\, kg$ weight. He wants to swim in a river with the help of a wooden log. If relative density of wood is $0.6$, what is the minimum volume of wooden log? (density of river water is $1000\, kg/m^3$)
AIIMS 2010, Medium
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Archimedes principal states that weight of body displaced by $liquid=upthrust.$
$60 \times g + V \times 0.6 \times {10^3}\,g = V \times 1000\,g$
$60 + 600\,V = 1000V$
$60 = 400V$
$V = \frac{{60}}{{400}} = \frac{3}{{20}}{m^3}$
Where, $V$ is the volume of wooden log.
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