A car moving along a straight highway with speed of 126 mathrm{km} h^{-1} is brought to a stop withi

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2.Motion in Straight Line

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A car moving along a straight highway with speed of $126 \;\mathrm{km} h^{-1}$ is brought to a stop within a distance of $200\; \mathrm{m}$. What is the retardation of the car (assumed uniform in $m/s^2$) ?

A

$6.150$

B

$3.0625$

C

$1.5312$

D

$1.4141$

Solution

$u=126 \mathrm{km} / \mathrm{h}=126 \times \frac{5}{18} \mathrm{m} / \mathrm{s}=35 \mathrm{m} / \mathrm{s}$

$v=0$

$s=200 m$

Newton's Equation of motion $v^{2}-u^{2}=2 a s$

$0^{2}-35^{2}=2 a(200)$

$a=-3.0625 \mathrm{m} / \mathrm{s}^{2}$

Standard 11

Physics

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