Newton Law's

I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. 

II. The relationship between an object's mass m, its acceleration a, and the applied force F is

F = ma.

Acceleration and force are vectors in this law the direction of the force vector is the same as the direction of the acceleration vector. 

III. For every action there is an equal and opposite reaction.  

"Based on the second law we consider that 1 N(Newton) is the net force that's requared for an object of 1 kg mass to travel with acceleration of 1 m/s²."

1N ≡ 1kg m/s²   

   1N ≈ 0.22481 lb_F 

1pdl ≡ 1 lb·ft/s²

1 pdl = 0.138254954376 N