A box starts from rest at the top of a rough slope. It then slides down the slope. The box has a weight of $20\,\text{N}$. The slope measures $4.0\,\text{m}$ in length and $2.0\,\text{m}$ in height. As the box moves down the slope, it does $10\,\text{J}$ of work against friction. What is the speed of the box when it reaches the bottom of the slope?
- A$5.4\,\text{m s}^{-1}$
- B$6.3\,\text{m s}^{-1}$
- C$7.1\,\text{m s}^{-1}$
- D$9.5\,\text{m s}^{-1}$