An airplane reaches a velocity of 71m/s^2 when it takes off. What must its acceleration be if the runway is 1.0km long

Vf^2 = Vo^2 + 2a*d,

a = (Vf^2-Vo^2) / 2d,
a = ((71)^2-0) / 2000 = 2.52 m/s^2.