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Commercial unit of energy - class-IX
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A two kilowatt motor pumps out water from a well 10 meter deep. The quantity of water pumped out per hour is ( g = 10 $m/s^2$)
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A
$72 \times 10^3$ kg
💡 Explanation:
Two kilowatt motor pump means that 2kJ wotk is done in $1$ sec
Let $m$ be the mass of water that is pumped out
Work done , $W=2\ kJ=2000\ J$
Time taken , $t=1 sec$
Displacement of water , $h= 10\ m$
As in this case $W=mgh $
$\implies 2000= m\times 10\times 10$
$\implies m=20\ kg$
Quantity of water pumped out per sec , $m=20\ kg$
$\therefore \text{ Quantity of water that is pumped out per hour }= m\times 3600=20\times 3600= 72\times 10^3 \ kg $