BRAINCAKEConservation of Momentum in Two Dimensions
The principle of conservation of momentum: in a closed system (one with no external resultant force), the total momentum before an interaction equals the total momentum after it.
Because momentum is a vector, this applies to direction as well as size. In two dimensions it means:
• the vector sum of the momenta before = the vector sum of the momenta after
• equivalently, momentum is conserved separately in any two perpendicular directions (x and y)
This applies to collisions, where objects hit and may stick together or bounce apart, and to explosions, where objects start together and fly apart. An object at rest that explodes has zero total momentum, so the momenta of the pieces must add up to zero.
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