A particle moves in a straight line with a retardation (SI units). Its speed is at . The time taken for the speed to fall to is

Answer and explanation

Correct answer: D.

  1. Step 1: Express deceleration as differential rate of velocity change: .
  2. Step 2: Separate variables and integrate from initial speed at to final speed at time : .
  3. Step 3: Evaluate the limits: .
Answer
.
Why not the others: assumes constant deceleration at the initial maximum value .

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