A particle of mass m is driven by a machine that delivers a constant power k watts. If the particle starts…
A particle of mass is driven by a machine that delivers a constant power watts. If the particle starts from rest the force on the particle at time is:
Solution
$\begin{aligned}
& F v=\text{constant}=k \\
& \text{So}, \\
& \frac{m dv}{d t} v=k \\
\Rightarrow & \int v dv=\int \frac{k}{m} dt \\
\Rightarrow & \frac{v^2}{2}=\frac{k}{m} t \\
\Rightarrow & v=\sqrt{\frac{2 k}{m} t}
\end{aligned}$
Now,
$\begin{aligned}
& F=\frac{m dv}{d t} \\
& =m \sqrt{\frac{2 k}{m}} \frac{1}{2} t^{-\frac{1}{2}} \\
& =\sqrt{\frac{m k}{2}} t^{-\frac{1}{2}}
\end{aligned}$
Asked in: NEET 2015 (Phase 1)
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