A train is travelling at a speed of 90, km ,h^{-1} . Brakes are applied so as to produce a uniform a

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7. MOTION

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A train is travelling at a speed of $90\, km \,h^{-1}$. Brakes are applied so as to produce a uniform acceleration of $- 0.5\, m s^{-2}$. Find how far(in $m$) the train will go before it is brought to rest.

A

$625$

B

$225$

C

$500$

D

$750$

Solution

Initial speed of the train, $u =90\, km / h =25\, m / s$

Final speed of the train, $v =0$ (finally the train comes to rest)

Acceleration $=-\,0.5 \,m s ^{-2}$

According to third equation of motion:

$v ^{2}= u ^{2}+2 as$

$(0)^{2}=(25)^{2}+2(-0.5)\, s$

Where, $s$ is the distance covered by the train

$s=\frac{25^{2}}{2(0.5)}=625\,m$

The train will cover a distance of $625\, m$ before it comes to rest.

Standard 9

Science

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