When we say directly northeast that is equivalent to 45˚ north of east.
First let us determine the north and east components of the acceleration using cos and sin functions:
North = 2.18 * sin 45
East = 2.18 * cos 45
Then we set to determine the east component of the plane’s displacement by calculating using the formula:
d = vi * t + ½ * a * t^2
d = 135 * 18 + ½ * 2.18 * cos 45 * 18^2
d = 2430 + 353.16 * cos 45 = 2679.72 m
Calculating for the north component:
North = ½ * 2.18 * sin 45 * 18^2
North = 249.72 m
Hence magnitude is:
Magnitude = sqrt (2679.72^2 + 249.72^2)
Magnitude = 2,691. 33 m
Calculating for angle:
Tan θ = North ÷ East
Tan θ = 249.72 m ÷ 2679.72 m
θ = 5.32°
So the plane was flying at 2,691. 33 m at 5.32°