A bird flies for 4s with a velocity v=(t-1) m/s . . .

Question : A bird flies for 4s with a velocity v=(t-1) m/s in a straight line. Calculate :

(a) acceleration at t=2s, is it uniform or non uniform?

(b) the displacement of the bird in 4s.

Doubt by Girisha

Solution : 

(a) v=(t-1) m/s
differentiating both sides wrt time t.
a=dv/dt
a=d(t-1)/dt
a=1 m/s²

Clearly the acceleration is independent of time hence it is a uniform acceleration. 

(b) We know, 
v=dx/dt
dx=vdt
integrating both sides within proper limits

Hence, displacement in 4sec is equal to 4 m.