At what temperature, an oxygen molecule has the same rms velocity as the hydrogen molecule has at 20 K ?

A hole of diameter 5 cm is drilled in a metal sheet at $30^{\circ} \mathrm{C}$. The linear expansion of metal is $2 \times 10^{-5} \mathrm{~K}^{-1}$. The diameter of the hole when the temperature is raised to $230^{\circ} \mathrm{C}$, is equal to

A metal cube absorbs 2100.0 J of heat when its temperature is raised by $2^{\circ} \mathrm{C}$. If the specific heat of the metal is $900 \mathrm{~J} \mathrm{~kg}^{-1} \mathrm{~K}^{-1}$, then the mass of the cube is

The net work done by an ideal gas going through the cycle as shown in the $p-V$ diagram below is