A body of mass m subject to a force F undergoes an acceleration a that has the same direction as the force and a magnitude that is directly proportional to the force and inversely proportional to the mass, i.e., F = ma. Alternatively, the total force applied on a body is equal to the time derivative of linear momentum of the body.

Or, the applied unbalanced force is proportional to rate of change of momentum.

F is proportional to p2 - p1 / t

F is proportional to mv - mu / t

F is proportional to m [v - u / t]

F is proportional to m * a

F = k * ma (as k = 1)

F = Mass * acceleration

= kg m/s2

= N (newton)

F = Force

p2 = Final Momentum

p1 = Initial Momentum

m = Mass

u = Initial Velocity

v = Final Velocity

t = Time taken for u to become v

a = Acceleration

k = constant