A air bubble of radius 1 cm in water has an upward acceleration $9.8 \mathrm{~cm} \mathrm{~s}^{-2}$. The density of water is 1 gm $\mathrm{cm}^{-3}$ and water offers negligible drag force on the bubble. The mass of the bubble is ( $\mathrm{g}=980 \mathrm{~cm} / \mathrm{s}^2$ )
