# When would impulse be used?

1. Aug 18, 2009

### mahela007

In what kind of instances would the quantity of impulse be used? My text book says that it's when very large forces act for very short times but how would that help us calculate the force OR the time?

2. Aug 18, 2009

### Shooting Star

It is precisely when we cannot or do not need to calculate the force or the time for which it acts that we use the concept of impulse. The impulse is the integral of the force with respect to time and can be proved to be equal to the change in momentum. Here are some good sites for preliminary reading:

http://id.mind.net/~zona/mstm/physics/mechanics/momentum/introductoryProblems/momentumSummary2.html [Broken]
http://www.glenbrook.k12.il.us/gbssci/phys/Class/momentum/u4l1b.html [Broken]

Last edited by a moderator: May 4, 2017
3. Aug 18, 2009

### arildno

A classical example is in the analysis of collisions.

4. Aug 18, 2009

### Staff: Mentor

When I was in school, I was "into" model rocketry for a while. Solid-fuel model rocket engines were rated in terms of the total impulse they produced, between ignition and burnout. The actual thrust (force) exerted varied widely during the burn period, but the burn period was short enough that you could use the total impuse to calculate good estimates of launch speed, maximum height of trajectory, etc.

5. Aug 20, 2009

### mahela007

Thanks

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