A man is 45 m behind the bus when the bus starts acceleration from rest with acceleration `2.5(m)/(s^2)`. With what minimum velocity should man start running to catch the bus?

Options

A. `12 m//s`
B. `14 m//s `
C. ` 15 m//s `
D. ` 16 m//s `

Answer

C

Explanation

man catch the bus after 't' sec . So he will cover distance ut. Similarly distance travelled by the bus will be` (1)/(2) at^(2) ` . For the given condition ` u= t=45 +(1)/(2) a t^(2) =45 +1.25 t^(2) " "rArr 1.25 t^(2) -ut +45 =0`
If the man catches the bus, at some time t, this quadratic should have real roots.` rArr u^(2) -4(1.25) (45) ge 0 rArr u ge 15m //s `