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NDA 1 2025 GAT, question 145

Topic: Physics

Q145

Which one of the following equations related to the motion of an object is NOT correct ? (Symbols carry their usual meanings)

  1. (a) s=ut+12at2s = ut + \frac{1}{2}at^{2}
  2. (b) u=v−atu = v - at
  3. (c) u2−v2=2asu^{2} - v^{2} = 2asCorrect answer
  4. (d) Distance travelled during nthn^{th} second =u+12a(2n−1)= u + \frac{1}{2}a(2n - 1)

Solution.

Answer: (c) u2−v2=2asu^{2} - v^{2} = 2as

  1. The correct squared-velocity relation is v2−u2=2asv^{2} - u^{2} = 2as.
  2. Equivalently, u2−v2=−2asu^{2} - v^{2} = - 2as, so option (c) has the wrong sign.
  3. The other formulae are the standard constant-acceleration relations; the nth-second expression follows by subtracting the displacements at times nn and n−1n - 1.