Motion in a Straight Line · NEET Preparation Physics

A particle moves along a straight line such that its displacement x varies with time t as x = sqrt{t} + 1. The acceleration of the particle is propor…

Practice question from Motion in a Straight Line (NEET Preparation Physics), with the correct answer and a step-by-step solution.

hard · MCQ · Q-CC8F1A

A particle moves along a straight line such that its displacement xx varies with time tt as x=t+1x = \sqrt{t} + 1. The acceleration of the particle is proportional to:

  1. A.v
  2. B.v^2
  3. C.v^3Correct answer
  4. D.1/v

Solution

Given x=t1/2+1x = t^{1/2} + 1. Velocity v=dxdt=12t−1/2v = \frac{dx}{dt} = \frac{1}{2}t^{-1/2}. Acceleration a=dvdt=12(−12)t−3/2=−14t−3/2a = \frac{dv}{dt} = \frac{1}{2}\left(-\frac{1}{2}\right)t^{-3/2} = -\frac{1}{4}t^{-3/2}. Since v=12t−1/2v = \frac{1}{2}t^{-1/2}, we have t−1/2=2vt^{-1/2} = 2v, so t−3/2=(2v)3=8v3t^{-3/2} = (2v)^3 = 8v^3. Thus, a=−14(8v3)=−2v3a = -\frac{1}{4}(8v^3) = -2v^3, meaning a∝v3a \propto v^3.

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