this helped alot, but im just confused about how the momentum can be conserved yet energy is not?
are clipping voltages in the study design?
mod edit: merged posts.
Momentum is conserved because its fundamentally a different quantity than kinetic energy. In an isolated system, which most of the questions are framed in, momentum is always conserved because the net force on all objects is zero (that's the definition of an isolated system). Newton's 2nd law in its original form states that
Thus since the net force is zero, in a collision the change in momentum is zero, so it's conserved (the change in momentum in this equation refers to the total momentum of the system, not the momentum of an object).
Kinetic energy isn't conserved because there are many forms of energy. Some of the original kinetic energy in your system will be present after a collision, however some of it is lost as sound, heat, etc. The TOTAL amount of energy in an isolated system is conserved, but the kinetic energy present at the beginning could transform into another form.