A very broad elevator is going vertically upwards with a constant acceleration of $2 {\mathrm{ms}}^{-2}$. At the instant when its velocity is $4 {\mathrm{ms}}^{-1}$, a ball is projected from the floor of the lift with a speed of $4 {\mathrm{ms}}^{-1}$ relative to the floor at an angle of ${30}^{°}$. The time of flight of the ball in the elevator is ($\text{g}=10 {\mathrm{ms}}^{-2}$)