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2.Motion in Straight Line
medium
A body initially at rest is moving with uniform acceleration $a$ . Its velocity after $n$ seconds is $v$ . The displacement of the body in last $2\,s$ is
A
$\frac{{2v(n - 1)}}{n}$
B
$\frac{{v(n - 1)}}{n}$
C
$\frac{{v(n + 1)}}{n}$
D
$\frac{{2v(n + 1)}}{n}$
Solution
Here, $a=\frac{v-u}{t}=\frac{v-0}{n}=\frac{v}{n}$
Displacement in last $2\, s$
$\mathrm{S}_{\mathrm{n}}-\mathrm{S}_{\mathrm{n}-2}=\frac{1}{2} \mathrm{an}^{2}-\frac{1}{2} \mathrm{a}(\mathrm{n}-2)^{2}$
${=2 \mathrm{a}(\mathrm{n}-1)=2 \frac{\mathrm{v}}{\mathrm{n}}(\mathrm{n}-1)}$
${=\frac{2 \mathrm{v}(\mathrm{n}-1)}{\mathrm{n}}}$
Standard 11
Physics