A lift is moving downwards with an acceleration equal to accelera… - Vidyadip

MCQ

A lift is moving downwards with an acceleration equal to acceleration due to gravity. A body of mass $m$ kept on the floor of the lift is pulled horizontally. If the coefficient of friction is $\,\mu $, then the frictional resistance offered by the body is

A
$mg$
B
$\mu mg$
C
$2\mu mg$
✓
Zero

✓

Answer

Correct option: D.

Zero

d
(d) $(N=\text { normal, } m=\text { mass of object, } a=$ acceleration of lift)

$m g-N=m a$

$N=m a-m g$

$(\text { given } a=g)$

therefore $N=0$

friction $=u . N$

hence friction $=u .0(\mathrm{N}=0)$

$=0$

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