False they attract.. Remember opposites attract!
You find the net force by subtracting.
Both options 5 and 6
Explanation:
Let us consider option 5,
In option 5 body is moving up with initial velocity lower than that of final velocity which gets accelerated. Therefore the acceleration is positive in this case.
Let us consider option 6,
In option 6 body is moving down with initial velocity lower than that of final velocity which gets accelerated. Therefore the acceleration is positive in this case.