A Cessna aircraft has a liftoff speed of 120 km/h.

(a) What minimum constant acceleration does the aircraft require if it is to be airborne after a takeoff run of 260 m? (m/s)

(b) How long does it take the aircraft to become airborne? (s)

2 equations in 2 unknowns

v = at
120 km/hr / 3600 s/hr = 0.033 km/s * 1000 m/km = 33.33 m/s
33.33 m/s = at
a = 33.33/t

then

d = 0.5at^2
260 m = 0.5 * 33.33/t * t^2 (Cancel a t)

260 = 16.67 t
t = 260/16.67
t = 15.60 s

then

a = 33.333/15.6 = 2.14 m/s^2

QED