A body is moving with uniform acceleration describes 40 m in the first 5 sec and 65 m in next 5 sec. Its initial velocity will be

Options

A. 4m/s
B. 2.5m/s
C. 5.5m/s
D. 11m/s

Answer

C

Explanation

`S = ut + 1/2 at^2`
first 5sec : t = 5sec
`40 = 5u + 1/2 a(5)^2 rArr 16 = 2u + 5a`
`t = 10 sec, S = 40+ 65 = 105m`
`=105 = 10u + 1/2 a (10)^2 rArr 21 = 2u + 10a`
By (ii)-2 x (i) <
`21 = 2u + 10a`
`32 = 4u + 10a`
`-11= -2u rArr u = 5.5 m//s`