Newton's 2nd law of motion can be described mathematically as:

F = ma

Where F is the force applied to an object, m is the mass of the object, and a is the resulting acceleration.  Thus we can see that if you apply a force to a constant mass object, the object will undergo acceleration.  The acceleration felt by this object is simply a = F/m.  Conversely, if a mass is experiencing an acceleration (such as the acceleration due to gravity), a force equal to F = ma is felt by the mass.