Newton’s Second Law revisited, Impulse , Grade 11 physics
You have learned about Newton’s Second Law of motion earlier in this chapter. Newton’s Second Law describes the relationship between the motion of an object and the net force on the object. We said that the motion of an object, and therefore its momentum, can only change when a resultant force is acting on it. We can therefore say that because a net force causes an object to move, it also causes its momentum to change. We can now define Newton’s Second Law of motion in terms of momentum.

Definition: Newton’s Second Law of Motion (N2)
The net or resultant force acting on an object is equal to the rate of change of momentum.
Mathematically, Newton’s Second Law can be stated as:

F$_{net}$ = $\dfrac{\Delta p}{\Delta t}$​

Impulse

Impulse is the product of the net force and the time interval for which the force acts. Impulse is defined as:

Impulse = F · ∆t (12.8)​

However, from Newton’s Second Law, we know that

F = ∆p/∆t => F · ∆t = ∆p = Impulse​

Therefore,

Impulse = ∆p​

Impulse is equal to the change in momentum of an object. From this equation we see, that for a given change in momentum, F$_{net}$∆t is fixed. Thus, if Fnet is reduced, ∆t must be increased (i.e. a smaller resultant force must be applied for longer to bring about the same change in momentum). Alternatively if ∆t is reduced (i.e. the resultant force is applied for a shorter period) then the resultant force must be increased to bring about the same change in momentum.

Xem thêm:
Physics 11.II Force, Momentum, Impulse

High School Students Studying the Sciences Physics​