The rate of change of momentum of a body is equal to the resultant force acting on the body and is in the same direction.
Newton's second law as originally stated in terms of momentum p
“An applied force is equal to the rate of change of momentum”.
![An applied force is equal to the rate of change of momentum An applied force is equal to the rate of change of momentum](https://www.livephysics.com/media/stories/equations/classicalmechanics/newtonslaw001.gif.pagespeed.ce.YhnNDr-xpE.gif)
The physical meaning of this equation is simply a mathematical definition of a force (rate of change of momentum is called a force).
whereWhen the mass m, of the object is constant, the mathematical result of differentiation of momentum becomes simply:
F is the force
p is the momentum
t is the time
v is the velocity
m is the mass
a = is the acceleration.
![Image Image](https://www.livephysics.com/media/stories/equations/classicalmechanics/xnewtonslaw002.gif.pagespeed.ic.QogFCdADbU.png)
![for constant mass for constant mass](https://www.livephysics.com/media/stories/equations/classicalmechanics/newtonslaw003.gif.pagespeed.ce.YCtUBnhsNS.gif)
If the mass m is measured in kilograms and the acceleration a is measured in meters per second squared, then the unit of force is kilogram × meter/second squared. This unit is called the Newton: 1 N = 1 kg x 1 m/s².
Newton's Second Law
![F=ma Newton's second law of motion F=ma Newton's second law of motion](https://www.livephysics.com/media/stories/equations/classicalmechanics/newtonslaw004.gif.pagespeed.ce.I-VfCEjRNm.gif)