They seem to be using this specific definition of impulse. However, this is a useful model for computing the effects of ideal collisions (such as in game physics engines). This sort of change is a step change, and is not physically possible. This type of impulse is often idealized so that the change in momentum produced by the force happens with no change in time. The term 'impulse' is also used to refer to a fast-acting force or impact. Wikipedia seems to shed some light on this: Their version of 'impulsive force' seems to be a specific definition, not the general physics definition.

This means that the spring is changing the momentum of the object, and thus would be an impulsive force, as per the definitions I'm aware of. The velocity of the object connected to the spring is constantly changing, and it's mass remains the same. A trivial example is a object suspended by a spring which is first extended, and left alone to oscillate up and down. It's fairly trivial to show that over time, springs absolutely can change the momentum of an object they interact with. Determining the impulse will tell you how much the momentum of the object changed over that time period. To me, that definition seems too specific and non-intuitive compared to the general concept of an 'impulse' in physics.Īn impulse in physics is typically defined as the integral of force over time.

Non impulsive force definition