According to galileo, this quantity is not needed to keep a body in motion under ideal conditions.

According to Galileo, quantity does not matter under ideal conditions. The ideal conditions to experiment under is when there is no air resistance only then it can be seen that the statement is true i.e. quantity is not a factor

If you drop a ball and a feather under the ideal condition i.e. no air resistance you will see that both the ball and feather which weigh different will fall at the same time

because growing process had stoped after 4-5 year