A car is moving along a straight line is brought to a stop within a distance of $200 \mathrm{~m}$ and in…
A car is moving along a straight line is brought to a stop within a distance of $200 \mathrm{~m}$ and in time 10s. The initial speed of the car is
$25 \mathrm{~ms}^{-1}$
$50 \mathrm{~ms}^{-1}$
$25 \mathrm{~ms}^{-1}$
$25 \mathrm{~ms}^{-1}$
Solution
Given, displacement of car, $s=200 \mathrm{~m}$
Time taken, $t=10 \mathrm{~s}$
Final velocity of car $=0$
Now using,
Average velocity $\times$ time $=$ Displacement or
$
\left(\frac{v+u}{2}\right) \times t=s
$
We get, $\quad\left(\frac{0+u}{2}\right) \times 10=200$
$
\Rightarrow \quad u=\frac{200 \times 2}{10}=40 \mathrm{~m} / \mathrm{s}
$
Hence, initial speed of car $=40 \mathrm{~m} / \mathrm{s}$