Answer:
The new acceleration becomes twice the pervious acceleration.
Explanation:
Given that,
Mass of the rock, m = 3 kg
Force, F = 1 N
We know that the force acting on an object is given by :
F = ma
a is acceleration of the rock
Put m = 3 kg and F = 1N,

If the force is doubled, F' = 2 N
So,
F'=ma'

So, the new acceleration becomes twice the initial acceleration.