/sci/ - Science & Math

/sci/ = the most painful 4chan board for anyone that actually works in /sci/.

two properties: conservation of mass, conservation of momentum. we only depart from reality here on the concept of momentum, where portal-logic dictates that momentum is invariant of direction (that is, changing direction of momentum requires no force applied.)

conservation of mass (equivalently, conservation of the rigid body shape) gives the top boxed equation. simple enough, anything going into the left portal has to come out the right.

conservation of momentum gives the second equation. important thing missed by many here is the basic principle of galilean invariance (left side sketch). the falling plunger on static cube is equivalent to a moving cube hitting a static plunger. if you don't understand this concept, i suggest you get off the internet and study.