Explanation:
Let [tex]s[/tex] be the distance of runway.
Let [tex]u[/tex] be the initial velocity of aeroplane.
Let [tex]v[/tex] be the initial velocity of aeroplane.
Let [tex]t[/tex] be the time taken by Susan.
Given,
[tex]u=4ms^{-1}[/tex]
[tex]v=30ms^{-1}\\t=15sec[/tex]
From the given information we can assume that no additional forces are acting.So,the acceleration is constant.
The length of runway will be minimum if the aeroplane takes off in [tex]15[/tex] seconds.
As we know from the equations of motion,
[tex]s=\frac{u+v}{2}\times t[/tex]
So,[tex]s=\frac{(4+30)}{2}\times 15=255m[/tex]
So,the minimum length of the runway required is [tex]255m[/tex]
