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7. MOTION
normal
A train is travelling at a speed of $90\, km h ^{-1}$. Breaks are applied so as to produce a uniform acceleration of $0.5\, m s ^{-2}$. Find how far the train will go before it is brought to rest.
Option A
Option B
Option C
Option D
Solution
Given $u=90 km h ^{-1}=5 \times \frac{90}{18}=25 m s ^{-1}, v=0$
$a=-0.5 m s ^{-1}, S =?$
Using
$v^{2}-u^{2}=2 a S$
$0-(25)^{2}=2 \times-0.5 \times 5$
or $S =625 m$
Standard 9
Science