Which Method Best Solves for Final Velocity of Object B After Collision?

[Seif]

If you have 2 objects that collide...A & B...and you have the mass and initial velocity of both, and the final velocity of A. What would be the better way of solving for the final velocity of B? Using KEi=Kef or Pi=Pf?

 

[HallsofIvy]

Since you are asked for velocity- a vector quantity, you will need to use "conservation of momentum". Energy is a "scalar" (a number) and while conservation of energy could tell you the speed of B, it can't tell you the direction.

If everything is in a straight line, it's still better to use conservation of momentum to get "left" or "right" correct.

 

[M98Ranger]

The better way of solving for the final velocity of B would depend on the specific situation and the information given. If both objects are moving in the same direction before the collision, then using the conservation of momentum equation (Pi=Pf) would be the most appropriate method. This is because the total momentum of the system (A and B combined) will remain the same before and after the collision.

On the other hand, if the objects are moving in opposite directions before the collision, then using the conservation of kinetic energy equation (KEi=Kef) would be more suitable. This is because in an elastic collision (where no energy is lost), the total kinetic energy of the system will remain the same before and after the collision.

In summary, the choice between using conservation of momentum or kinetic energy would depend on the specific scenario and the type of collision (elastic or inelastic). It is important to carefully consider the problem and choose the appropriate equation to solve for the final velocity of object B.