What is meant by the following statement?

"acceleration is inversely proportional to mass."

The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, n the same direction as the net force  and is inversely proportional to the mass of an object. Its Newtons second law

Twice the mass means one-half the acceleration , if the same net force acts on both objects

hope this helps

pe = weightxheight = 2000x1000=2,000,000joules

0.11 m/s and 0.28 m/s should be correct