Dear student,
A newton (N) is the international unit of measure for force. One newton is equal to 1-kilogram meter per second squared. In plain English, 1 newton of force is the force required to accelerate an object with a mass of 1 kilogram 1 meter per second per second.
1 N =1 Kg m / s2
Yes, if you applied from the outside also, it's value remains constant.
Actually, Newton is a standard unit of force.
So, what you are really measuring is force, rather than Newton.
Regards,