A machine which is 75 percent efficient, uses 12 joules of energy… - Vidyadip

MCQ

A machine which is $75$ percent efficient, uses $12 $ joules of energy in lifting up a $1\, kg$ mass through a certain distance. The mass is then allowed to fall through that distance. The velocity at the end of its fall is (in $m{s^{ - 1}})$

A
$\sqrt {24} $
B
$\sqrt {32} $
✓
$\sqrt {18} $
D
$\sqrt 9 $

✓

Answer

Correct option: C.

$\sqrt {18} $

c
(c)Potential energy of a body $= 75J$ of $ 12 \%$
$mgh = 9 \,J$

==> $h = \frac{9}{{1 \times 10}} = 0.9m$
Now when this mass allow to fall then it acquire velocity
$v = \sqrt {2gh} = \sqrt {2 \times 10 \times 0.9} = \sqrt {18} $m/s.

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