Hi there,

im currently working through Ian Millington's book “Game Physics Engine Development” and I've come across the term “unit of impulse” and can't wrap my head around what it means. My initial thought was that it means the literal physical unit of an impulse, something like N (newton) or so. But judging from the context, it means something else.

In the book, an impulse is described as “a force applied over a very short period of time” and it, instead of impacting the acceleration of an object, directly changes the velocity of the object.

It could also mean something analogue to a unit vector or a unit cube, so something with the value 1 which in terms of impulses could mean an impulse vector with the magnitude of 1.

Can anyone help me clarify that?

I think “per unit of impulse” just means “as a formula based on impulse.”

If you then use “one” as the input impulse, the output of that formula is the change in velocity per “unit” of impulse.

Of course, there are many units – pound times minute; Newton times second; kilogram-force times hour; and so on for impulse; inches-per-minute; meters-per-second; furlongs-per-fortnight; and so on for velocity. You have to pick one on each side, and stick to it. (Hint: Newtons times second and meters per second will probably make the math simpler.)

@hplus0603 Sounds good. Reading on had me feel the same way. Thanks for your reply!