A car starts accelerating with an acceleration of 13 m/s2 when its speed was 18 km/h. If the displacement of car in nth minute after it starts accelerating is 4.8 km, then n is:
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Solution
Given acceleration of car is 13 m/s2=60×603 m/min2 =36003=1200 m/min2
Initial velocity =18km/h=1800060=300 m/min
Using, S=u+a2(2n−1) 4.8(1000)=300+a2(2n−1) 4800=300+12002(2n−1) =2×45001200=2n−1 ⇒n=4.2≈4th minute.