A basketball player throws a ball straight downwards at a speed of $2.4\,\text{m s}^{-1}$ from a height of $0.90\,\text{m}$. The effect of air resistance can be ignored. What speed does the ball have when it reaches the ground?
- A$4.2\,\text{m s}^{-1}$
- B$4.8\,\text{m s}^{-1}$
- C$18\,\text{m s}^{-1}$
- D$23\,\text{m s}^{-1}$