A wooden plank is arranged horizontally and pivots at one end, as illustrated. Its mass is $100\,\text{kg}$ and its length is $10\,\text{m}$. The plank’s centre of gravity lies $4\,\text{m}$ from the pivot. What is the moment of the plank’s weight about the pivot?
- A$4 \times 10^2\,\text{N m}$
- B$5 \times 10^2\,\text{N m}$
- C$4 \times 10^3\,\text{N m}$
- D$5 \times 10^3\,\text{N m}$