Kaplan physics momentum questions

[Mantis Toboggin]

These two questions have been bothering me bigtime:

1.) Why is this an elastic collision?

Two calls collide and then move away from each other with the same speed but reverse directionality.

Elastic coll= equal momentum and KE. The KE part is all well and good (since v^2 will mean the total KE is conserved). But I plugged in some values to see if momentum is conserved, and it was not. Momentum is a vector value, and for whatever values you plug in, you will get

-x= +x , which would imply that the momentums were different. However Kaplan says that this IS an elastic collision. Am I just misreading the question, or did they make an error here?

2.) The key things I know about momentum are the 3 types of collisions, and the conditions that follow (KE conserved, not fully conserved, etc.) and that momentum is conserved given no external forces.

But I've come across some students saying we need to know what happens when a small object hits a large one, two equal sized objects hit one another, etc. Not sure exactly what they meant by this, could use some clarification as to what the MCAT implications are here

---

Members don't see this ad.

 

[SpaceBuff12]

These two questions have been bothering me bigtime:

1.) Why is this an elastic collision?

Two calls collide and then move away from each other with the same speed but reverse directionality.

Elastic coll= equal momentum and KE. The KE part is all well and good (since v^2 will mean the total KE is conserved). But I plugged in some values to see if momentum is conserved, and it was not. Momentum is a vector value, and for whatever values you plug in, you will get

-x= +x , which would imply that the momentums were different. However Kaplan says that this IS an elastic collision. Am I just misreading the question, or did they make an error here?

The total momentum of the system is conserved.

2.) The key things I know about momentum are the 3 types of collisions, and the conditions that follow (KE conserved, not fully conserved, etc.) and that momentum is conserved given no external forces.

But I've come across some students saying we need to know what happens when a small object hits a large one, two equal sized objects hit one another, etc. Not sure exactly what they meant by this, could use some clarification as to what the MCAT implications are here

If momentum is conserved and enough information is given you could solve: m1vi1+m2vi2 = m1vf1+m2vf2.