$A$ car is moving with a constant speed of $20\,m/s$ on a circular horizontal track of radius $40\,m$. $A$ bob is suspended from the roof of the car by a massless string. The angle made by the string with the vertical will be: (Take $g = 10\,m/s^2$)

$A$ man of mass $75\, kg$ is standing in an elevator which is moving with an acceleration of $5\, m/s^2$ in the upward direction. The apparent weight of the man will be ........... $N$ $(g = 10\, m/s^2)$.

$A$ 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 ......... $kg$.

Three masses $M = 100 \, kg$,$m_{1} = 10 \, kg$,and $m_{2} = 20 \, kg$ are arranged in a system as shown in the figure. All the surfaces are frictionless and strings are inextensible and weightless. The pulleys are also weightless and frictionless. $A$ force $F$ is applied on the system so that the mass $m_{2}$ moves upward with an acceleration of $2 \, m/s^{2}$. The value of $F$ is $...... \, N$. (Take $g = 10 \, m/s^{2}$)

$A$ spring balance is attached to the ceiling of a lift. $A$ man hangs his bag on the spring and the spring reads $49 \, N$,when the lift is stationary. If the lift moves downward with an acceleration of $5 \, m/s^2$,the reading of the spring balance will be .......... $N$.

$A$ weight is suspended from the ceiling of a lift by a spring balance. When the lift is stationary,the spring balance reads $W$. If the lift suddenly falls freely under gravity,the reading on the spring balance will be