A body starts from rest and moves for ' n ' seconds with uniform acceleration ' a ', its velocity after n seconds is 8 m / s . The displacement of the body in last 3 seconds is 15

Question

A body starts from rest and moves for ' n ' seconds with uniform acceleration ' a ', its velocity after n seconds is 8 m / s . The displacement of the body in last 3 seconds is 15 m . Find the value of a ​ .

TestHub · Accepted Answer

v = u + at ​ v = 0 + an = 8 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ an = 8 s = 0 + 2 1 ​ a n 2 15 = 2 1 ​ a [ n 2 − ( n − 3 ) 2 ] 2 1 ​ a [ 6 n − 9 ] = 15 2 1 ​ × n 8 ​ × 3 [ 2 n − 3 ] = 15 4 ( 2 n − 3 ) = 5 n 8 n − 12 = 5 n n = 4 a n ​ = 4 8 ​ = 2 m / se c 2 .

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