Motion in a Straight Line - Result Question 5
5. 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: 5. (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
$\Rightarrow s=\frac{v^{2}-u^{2}}{2 a}$
$\Rightarrow s=\frac{(40)^{2}-(0)^{2}}{2 \times 2}=\frac{1600}{4}=400 m$.
