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 μ then the frictional resistance offered by the body is :

Question

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 μ then the frictional resistance offered by the body is : (A)  mg  (B)  μ mg  (C)  2μ mg  (D) zero

Tardigrade Admin · Accepted Answer

Lift is moving down with acceleration due to gravity, hence, it falls freely. In this case apparent weight of body in lift is zero, therefore no frictional resistance will be offered by the body.

Q. 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 $μ$ then the frictional resistance offered by the body is :

$m g$

$μ m g$

$2 μ m g$

zero

Lift is moving down with acceleration due to gravity, hence, it falls freely.
In this case apparent weight of body in lift is zero,
therefore no frictional resistance will be offered by the body.

Q. 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 μ then the frictional resistance offered by the body is :

mg

μmg

2μmg