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2.Motion in Straight Line
hard
The velocity $(v)$ of a particle moving along $x$-axis varies with its position $x$ as shown in figure. The acceleration $(a)$ of particle varies with position $(x)$ as

A
$a^2=x+3$
B
$a=2 x^2+4$
C
$2 a=3 x+5$
D
$a=4 x-8$
Solution
(d)
$a=\frac{v d v}{d x}$
$\frac{d v}{d x} \rightarrow$ slope
So, $\frac{-4}{2}=-2$
Intercept $=+4$
$a \rightarrow$ Negative
So, $a=\frac{v d v}{d x}$
Relation between $V$ and $x$
$\Rightarrow \frac{v-4}{x-0}=\frac{0-4}{2-0}$
$\Rightarrow \frac{v-u}{x}=\frac{-4}{2}$
$\Rightarrow v-4=-2 x$
$\Rightarrow v=-2 x+4$
$\Rightarrow \frac{d v}{d x}=-2$
$\Rightarrow a=\frac{v d v}{d x}=(-2 x+4)(-2)$
$\Rightarrow a=4 x-8$
Standard 11
Physics