Step 1: Recall the formula for rms speed.
The rms speed of a gas is
\[
v_{\text{rms}}=\sqrt{\frac{3RT}{M}}
\]
Thus,
\[
v_{\text{rms}}\propto \frac{1}{\sqrt{M}}
\]
where
\[
M
\]
is the molar mass of the gas.
Step 2: Write the molar masses.
For oxygen gas:
\[
M_{O_2}=32
\]
For hydrogen gas:
\[
M_{H_2}=2
\]
Step 3: Form the ratio of rms speeds.
\[
\frac{v_{H_2}}{v_{O_2}}
=
\sqrt{\frac{M_{O_2}}{M_{H_2}}}
\]
\[
=
\sqrt{\frac{32}{2}}
\]
\[
=
\sqrt{16}
\]
\[
=4
\]
Step 4: Find the rms speed of hydrogen.
Given,
\[
v_{O_2}=500\,\text{m s}^{-1}
\]
Therefore,
\[
v_{H_2}=4\times 500
\]
\[
v_{H_2}=2000\,\text{m s}^{-1}
\]
Step 5: Final conclusion.
Hence, the rms speed of hydrogen is
\[
\boxed{2000\,\text{m s}^{-1}}
\]