Read before next class, if you have time.


MOMENTUM!

We come up with momentum through Newton's 2nd Law:


F = ma
F = m Dv/t

Rearranging:

Ft = m Dv

So this means that (on the left side) Force x time = (on the right side) mass x change in speed.

Or simply:

Ft = mv

This interaction of force happens during a so-called "collision" or "explosion".

Ft is defined as "impulse" and mv is defined as "momentum."  


Note that the above equation helps explain how boxing gloves and airbags work – they increase the time of contact, thereby decreasing the average force delivered to the object.

Please watch these clips:

https://www.youtube.com/watch?v=3vDQm0qIYi0

https://www.youtube.com/watch?v=y3InF19dzlM
Momentum (which is the mv part of the above equation) is another way to describe (mathematically) how objects collide or explode – generally involving contact of some sort.

p = mv

No new unit here, just:  kg-m/s

Momentum is transferred (and always conserved) during collisions or explosions, such that:

Initial momentum = Final momentum
pi = pf

Momentum is always conserved in collisions or explosions.  The direction is important.  And we think of the momentum of the entire system.

In other words, when things collide, the total of the (mv) in the beginning is equal to the total (mv) after the collision.  This is also true in explosions.

If you're feeling ambitious:

http://www.physicsclassroom.com/class/momentum



And play with these gizmos, if you have time:

https://www.explorelearning.com/index.cfm?method=cResource.dspResourceExplorer&browse=Science/Grade+9-12/Physics/Collisions

https://www.explorelearning.com/index.cfm?method=cResource.dspView&ResourceID=12








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