Acceleration and free fall problem

[cheerspens]

Homework Statement

A jumbo jet needs to reach a speed of 300 km/hr on a runway for take off. Assuming a constant acceleration and a runway 2 km long, what minimum acceleration from rest is required to get the jet in the air?

Homework Equations

I tried using the equation:
2a(X-Xo)=V^2+Vo^2

But there is also:
X=Xo+Vot+(1/2)at^2
V=Vo+at

The Attempt at a Solution

I set up the following variable list:
Xo=1.5 Vo=?
X=21.5 V=0
t=? a=-9.8

I plugged these values into the equations mentioned above to get a final answer of 2250km/hr^2 for the acceleration needed.

 

[w3390]

The first equation you have written (Vf^2 - Vi^2 = 2*a*x) should work. Assume the plane is starting from rest. This will give you all the variables except for the one you're looking for.