The displacement of a particle at the time $\mathrm{t}$ is given by $\quad s=\sqrt{1+t}$, then its…

The displacement of a particle at the time $\mathrm{t}$ is given by $\quad s=\sqrt{1+t}$, then its acceleration 'a' is proportional to
  1. square of the velocity
  2. $\sqrt[3]{S}$
  3. $\sqrt{S}$
  4. cube of the velocity

Solution

Given $s=\sqrt{1+t}$ Differentiating with respect to $\mathrm{t}$, we get $\begin{aligned} \mathrm{v} &=\frac{\mathrm{ds}}{\mathrm{dt}}=\frac{1}{2 \sqrt{1+\mathrm{t}}} \\ \mathrm{a} &=\frac{\mathrm{d}^{2} \mathrm{~s}}{\mathrm{dt}^{2}}=\frac{1}{2} \frac{\mathrm{d}}{\mathrm{dt}}(1+\mathrm{t})^{\frac{-1}{2}}=\frac{1}{2}\left(-\frac{1}{2}\right)(1+\mathrm{t})^{\frac{-3}{2}} \\ &=\left(\frac{-1}{4}\right)\left(\frac{1}{(1+\mathrm{t})^{\frac{3}{2}}}\right)=-2\left(\frac{1}{\left[(1+\mathrm{t})^{\frac{1}{2}}\right]^{3}}\right)=-2\left(\frac{1}{2 \sqrt{1+\mathrm{t}^{2}}}\right)^{3}=-2 \mathrm{v}^{3} \end{aligned}$

Asked in: MHT CET 2020 (12 Oct Shift 1)

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