A body is moving unidirectionally under the influence of a constant power source. Its displacement in time…

A body is moving unidirectionally under the influence of a constant power source. Its displacement in time $\mathrm{t}$ is proportional to :
  1. $t$
  2. $t^{3 / 2}$
  3. $t^2$
  4. $t^{2 / 3}$

Solution

$\begin{aligned} & P=\operatorname{constant} \Rightarrow \mathrm{FV}=\text { constant } \\ & \Rightarrow \mathrm{m} \frac{\mathrm{dV}}{\mathrm{dt}} \mathrm{V}=\text { constant } \\ & \int_0^{\mathrm{V}} \mathrm{VdV}=(\mathrm{C}) \int_0^{\mathrm{t}} \mathrm{dt} \\ & \left(\frac{\mathrm{V}^2}{2}\right)=\mathrm{Ct} \\ & \mathrm{V} \propto \mathrm{t}^{1 / 2} \\ & \frac{\mathrm{ds}}{\mathrm{dt}} \propto \mathrm{t}^{1 / 2} \\ & \int_0^{\mathrm{S}} \mathrm{ds}=\mathrm{K} \int_0^{\mathrm{t}} \mathrm{t}^{1 / 2} \mathrm{dt} \\ & \mathrm{S}=\mathrm{K} \times \frac{2}{3} \mathrm{t}^{3 / 2} \\ & \mathrm{~S} \propto \mathrm{t}^{3 / 2}\end{aligned}$ $\therefore$ displacement is proportional to $(\mathrm{t})^{3 / 2}$

Asked in: JEE Main 2024 (05 Apr Shift 2)

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