A particle is moving along \(x\) axis and its velocity (v) vs position \((x)\) graph is a curve as shown in…

A particle is moving along \(x\) axis and its velocity (v) vs position \((x)\) graph is a curve as shown in the figure. Line \(A P B\) is normal to the curve at point \(P\). Find the instantaneous acceleration of the particle at \(x=3.0 \mathrm{~m}\).

Solution

Let the velocity of the particle at \(x=3.0 \mathrm{~m}\) be \(v_{0}\). The slope of line \(A P B=-\frac{v_{0}}{1}\)
As the line \(A P B\) is normal to the curve at point \(P\), hence the slope of tangent at \(P=\frac{1}{v_{0}}\)
It means the slope of \(v-x \operatorname{graph}\left(\frac{d v}{d x}\right)_{P}=\frac{1}{v_{0}}\)
...(i)
But we define acceleration as \(a=v \frac{d v}{d x}\) ...(ii)
But at \(x=3.0 \mathrm{~m}, v=v_{0}\)
and \(\frac{d v}{d x}=\left(\frac{1}{v_{0}}\right) a=v_{0}\left(\frac{1}{v_{0}}\right)=1 \mathrm{~m} / \mathrm{s}^{2}\)
Hence \(a=v_{0}\left(\frac{1}{v_{0}}\right)=1 \mathrm{~m} / \mathrm{s}^{2}\)

Asked in: JEE Mains - Motion In One Dimension - Chapter Test

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