A car is standing $\mathrm{200\hspace{0.17em}}\mathrm{m}$ behind a bus, which is also at rest. The two start moving at the same instant but with different forward accelerations. The bus has acceleration $2 \mathrm{m} {\mathrm{s}}^{-2}$ and the car has acceleration $4\mathrm{\hspace{0.17em}}\mathrm{m} {\mathrm{s}}^{-2}$ . The car will catch up with the bus after time :