Memorize the famous formula: F = ma, or force - mass times acceleration. The units of force is newtons (N), also written out as Kg-m/s^2. The units of mass is kilograms, and acceleration is meters per seconds squared (m/s^2) So here you have:

F = ma

5x10^3 N = 1.1x10^3 Kg x a

Rearrange:

a = 5x10^3 N/1.1x10^3 m/s^2 = (5x10^3 Kg-m/s^2)/(1.1x10^3 Kg) = 4.5 m/s^2