How to calculate the net force in any direction on the box

subtract the lowest side from the opposite side

explanation:

7n< > 5n

subtract 5n from 7n to get 2n

a net force of 2n to the left

n = newtons

here we know that ball will drop down by total distance 3.2 m

so here we know that

now using kinematics

now in the same time it will cover horizontal distance of 0.75 m

so speed of the ball will be