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NDA 2 2024 GAT, question 123

Topic: Physics

Q123Not scored: no correct option as printed

A block of mass 2.0 kg2.0\text{ kg} slides on a rough horizontal plane surface. Let the speed of the block at a particular instant is 10 m/s10\text{ m/s}. It comes to rest after travelling a distance of 20 m20\text{ m}. Which one of the following could be the magnitude of the frictional force ?

  1. (a) 10 N10\text{ N}
  2. (b) 20 N20\text{ N}
  3. (c) 40 N40\text{ N}
  4. (d) 50 N50\text{ N}

Solution.

Not scored: no correct option as printed.

Answer: not scored. No option is correct as printed.

  1. Initial kinetic energy=½mv²=½×2×10²=100 J; final kinetic energy is zero.
  2. Friction therefore does 100 J of negative work over 20 m.
  3. Under the standard constant-friction model, its magnitude is 100/20=5 N, which is absent from the choices.
  4. If friction varies, only its average along the path is fixed at 5 N, and no unique instantaneous value is determined.