Motion In A Straight Line Ques 47
47. If a car at rest accelerates uniformly to a speed of $144 $ $km / h$ in $20$ $ s$, it covers a distance of
[1997]
(a) $2880 $ $m$
(b) $1440 $ $m$
(c) $400 $ $m$
(d) $20 $ $m$
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Answer:
Correct Answer: 47.(c)
Solution:
- (c) Initial velocity of car $(u)=0$
Final velocity of car $(v)=144 $ $km / hr=40 $ $ m / s$
Time taken $=20 $ $s$
We know that, $v=u+a t$
$40=a \times 20 \Rightarrow a=2$ $ m / s^{2}$
Also, $v^{2}-u^{2}=2$ as
$\Rightarrow s=\frac{v^{2}-u^{2}}{2 a}$
$\Rightarrow s=\frac{(40)^{2}-(0)^{2}}{2 \times 2}=\frac{1600}{4}=400 $ $m$.
BETA
