Question
A particle moves in a straight line with a constant acceleration . It changes its velocity from $10 \ ms^{-1 }$ to $ 20\ ms^{-1 }$ while passing through a distance $135\,m$ in $t$ second. The value of $t$ is $..........s$
✓
Answer
${v^2} - {u^2} = 2\,as$
Give $,v = 20\,m{s^{ - 1}},\,u = 10\,m{s^{ - 1}},\,s = 135\,m$
$\therefore a = \frac{{400 - 100}}{{2 \times 135}}$
$= \frac{{300}}{{270}}$
$= \frac{{10}}{9}m/{s^2}$
$v = u + at$
$\Rightarrow t = \frac{{v - u}}{a}$
$= \frac{{10m/s}}{{\frac{{10}}{9}m/{s^2}}}$
$= 9s$
Give $,v = 20\,m{s^{ - 1}},\,u = 10\,m{s^{ - 1}},\,s = 135\,m$
$\therefore a = \frac{{400 - 100}}{{2 \times 135}}$
$= \frac{{300}}{{270}}$
$= \frac{{10}}{9}m/{s^2}$
$v = u + at$
$\Rightarrow t = \frac{{v - u}}{a}$
$= \frac{{10m/s}}{{\frac{{10}}{9}m/{s^2}}}$
$= 9s$
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