According to Newton's Second Law of Motion, the force of an object is the product of its mass and acceleration. In other words,
F = ma
where, m is the object's mass and a is its acceleration.
If we magically double the mass of the object (m' = 2m), while keeping the force constant, its acceleration will change. If the new acceleration is a', then
F = m x a = m' x a' = (2m) x a'
or, a' = (m x a) / (2m) = a/2
Thus, the new acceleration will be half the original acceleration. The amount of force applied, in this case, is given as 10 N. If we are given the mass of the object, we can calculate the acceleration of the object (a = F/m).
Hope this helps.