\[(a)\;\frac{1}{2} s \quad (b)\;\frac{1}{3} s \quad (c)\;\frac{1}{4}s \quad (d)\;1 s\]

Component of velocity of ball relative to lift are

$u_x=4 \cos 30 ^{\circ}=2 \sqrt 3 m/s$

$u_y=4 \sin 30 ^{\circ}=2 m/s$

and acceleration of ball relative to lift is $a=10+2=12 m/s^2$ in negative y direction acting downwards.

Therefore Time of flight $T=\large\frac{2u_y}{a}$

$\qquad=\large\frac{2 \times 2}{12}$

$\qquad=\large\frac{1}{3}s$

Hence b is the correct answer.

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