An aeroplane lands at 216, km, h ^{-1} and stops after covering a runway of 2, km . Calculate accele

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7. MOTION

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An aeroplane lands at $216\, km\, h ^{-1}$ and stops after covering a runway of $2\, km .$ Calculate the acceleration and the time, in which its comes to rest.

Option A

Option B

Option C

Option D

Solution

$u=216 km h ^{-1}=60 m s ^{-1} ; \quad v=0 ; S =2 km$

$=2000 m ; a=? ; t=?$

$(i)$ Applying $v^{2}-u^{2}=2 aS,$ we have

$(0)^{2}-(60)^{2}=2 \times a \times 2000$

$a=-\frac{3600}{4000}=-0.90 m s ^{-2}$

$(ii)$ Applying $v=u+a t$

$0=60-0.90 t$

$0.90 t=60$ or $t=\frac{60}{0.90}=66.67 s$

Standard 9

Science

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