Mechanics: Inelastic Collisions Questions

[Jadenag]

Guys this is my first post on this site. Not sure If this is the correct thread but lmk?
Im having a tough time dealing with inelastic collisions. I am not entirely sure about the coefficient of restitution. I used to study a formula in Physics which was speed of aproach= Speed of separation for elastic collisions. Now in mechanics I am using the same formula but its velocity of approach=(-e)(velocity of separation) I believe. I firstly am having an issue with the directions of the velocities. Previously with elastic collisions Id just add the two in opposite directions and subtract the two in the same direction. Also. This coefficient of restitution. Is it also applicable to the Kinetic Energy before and after the inelastic collision? Is this also a formula: Initial K.E= (-e)(Final K.E) ? Thankyou.

 

[HallsofIvy]

"Adding in opposite directions and subtracting in the same direction" has nothing at all to do with "elastic" collisions. It has to do with whether you are dealing with collisions in one (on a line), two (on a plane), or three (in space) dimensions.

Yes, the total energy after the collision is equal to the total energy before the collision times the "coefficient of restitution". You will also need to use "conservation of momentum" to get directions right.