As you know, there are some equation in physics to describe the motion of the bodies under a constant acceleration, they are called "The Equations of motion".
one of there equation has got a relation between the final velocity, initial velocity, acceleration and the distance.
in symbols:
[tex]v^{2} _{f} =v^{2} _{i}+2ad[/tex]
where: [tex]v_{f}[/tex] is the final velocity, [tex]v_{i}[/tex] is the initial velocity, [tex]a[/tex] is the acceleration and [tex]d[/tex] is the distance
thus
[tex]11^{2}=5.0^{2}+2*3.0*d[/tex]
[tex]d=\frac{121-25}{6}=16m[/tex]
