Question

A lift is moving down with an acceleration equal 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. ${\mu }_{k}mg$
• B. $mg$
• C. $zero$
• D. ${\mu }_{k}m{g}^2$

Answer 1

The correct option is C $zero$

For freely falling body $g^{\prime }=g-a=g-g=0$
frictional force $=\mu N$
But, normal reaction $=m{g}^{\prime }=0$
$\therefore$ Frictional force $=\mu m{g}^{\prime }=0$