18 km h^-1 is equal to —

1. 10 m s^-1
2. 5 m s^-1
3. 18 m s^-1
4. 1.8 m s^-1

5 m s^-1

Reason — As,

$18 \text{ kmh}^{-1} = 18 \dfrac{\text{km}}{\text{h}} = \dfrac {18 \times 1000 m}{60 \times 60 \text{s}} \\[1em] \Rightarrow 18 \text{ kmh}^{-1} = \dfrac {18 \times 10 \text{m}}{6 \times 6 \text{s}} \\[1em] \Rightarrow 18 \text{\text{ kmh}}^{-1} = \dfrac {180 \text{ m}}{36 \text{ s}} \\[1em] \Rightarrow 18 \text{\text{ kmh}}^{-1} = 5 \text{ ms}^{-1}$

Hence, 18 km h^-1 is equal to 5 ms^-1.