The acceleration of an object increases by the force applied to it and decreases based on it's mass.

Explanation:

Force is defined as mass times acceleration.

Mathematically,          F = m × a

where             F = force

                       m = mass

                       a = acceleration

This shows that force is directly proportional to acceleration. So, when greater force is applied then acceleration will also increase.

Whereas acceleration is inversely proportional to mass. So, when there is increase in mass then there will be decrease in acceleration.