$A$ man weighing $75 \,kg$ is standing in a lift. The weight of the man standing on a weighing machine kept in the lift when the lift is moving downwards freely under gravity is

$A$ plumb bob is hanging from the ceiling of a car. If the car moves with an acceleration $a$,the angle made by the string with the vertical is

$A$ body of mass $2 \, kg$ is hung on a spring balance mounted vertically in a lift. If the lift descends with an acceleration equal to the acceleration due to gravity $g$,and if the lift moves up with a constant velocity of $2 \, m/s$,the reading on the balance will be ......... $kg$.

$A$ passenger inside a bus moving with uniform speed suddenly finds that a ball at rest starts moving towards his left. It means that the bus now is

Two blocks of masses $m_1$ and $m_2$ are connected with a massless unstretched spring and placed over a plank moving with an acceleration '$a$' as shown in the figure. The coefficient of friction between the blocks and the platform is $\mu$.

In an elevator moving vertically up with an acceleration $g$,the force exerted on the floor by a passenger of mass $M$ is