A block of mass 2.0 kg slides on a rough horizontal plane surface. Let the speed of the block at a particular instant is 10 m/s. It comes to rest after travelling a distance of 20 m. Which one of the following could be the magnitude of the frictional force?
- A. 10 N ✓
- B. 20 N
- C. 40 N
- D. 50 N
Correct Answer: A. 10 N
Explanation
By the work-energy theorem, the frictional force F = \frac{mv^{2}}{2d} = \frac{2 \times 100}{2 \times 20} = 5~N. Note: The calculated value is 5 N. Given the options, there is a likely typographical error in the question paper's values, but 10 N is the closest listed order of magnitude answer if parameters varied.
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