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7. MOTION
easy
A driver of a train travelling at $40\, m s ^{-1}$ applies the breaks as a train enters a station. The train slows down at a rate of $2\, m s ^{-2} .$ The platform is $400\, m$ long. Will the train stop in time ?
Option A
Option B
Option C
Option D
Solution
Given $u=40 m s ^{-1}, v=0, a=-2 m s ^{-2}, S =?$
Using equation, we have
$0=(40)^{2}+2(-2) S$
or $\quad 4 S=1600$ or $S=400 m$.
Thus, the train stops in $400 m$. Since the platform is $400 m$ long, therefore, the train just stops in time.
Standard 9
Science
