Water is driven through a hose-pipe at a mass flow rate of $90\,\text{kg per minute}$. The water leaves the hose-pipe horizontally at a speed of $20\,\text{m s}^{-1}$. Which force must be exerted by a person holding the hose-pipe to stop it moving backwards?
- A$30\,\text{N}$
- B$270\,\text{N}$
- C$1800\,\text{N}$
- D$10\,800\,\text{N}$