A ball of mass $m$ moves vertically downward and then strikes a horizontal floor with speed $u$. It bounces vertically upward with speed $v$. The impact lasts for a time $\Delta t$. What is the average resultant force exerted on the ball during the collision?
- A$\dfrac{mv - mu}{\Delta t}$ downwards
- B$\dfrac{mv - mu}{\Delta t}$ upwards
- C$\dfrac{mv + mu}{\Delta t}$ downwards
- D$\dfrac{mv + mu}{\Delta t}$ upwards