A shot-put champion speeds up a $7.0\,\text{kg}$ metal ball along a straight path. Starting from rest, the ball reaches a speed of $12\,\text{m s}^{-1}$ over a distance of $1.2\,\text{m}$. What is the average resultant force acting on the metal ball?
- A$70\,\text{N}$
- B$210\,\text{N}$
- C$420\,\text{N}$
- D$840\,\text{N}$