Conservation of Momentum in Elastic Collision

[missnur]

Hi all.

Pls help me with this question:

Two objects of mass m1=4kg and m2=2kg are moving with the same speed 1m/s towards each other before collision. Find the velocities of the 2 objects after collision if the collision is perfectly elastic.

Thank you all.

 

[Crazy Tosser]

Velocities as in speeds? Remember that velocity is speed plus direction, so you can't really say if your teacher wanted 2 positive answers, or one positive and one negative answer.

Anyway, we are not allowed to give out direct answers to homework questions, but I am pretty sure that the needed formula and examples is in your textbook ;)

Good luck!

 

[tiny-tim]

Welcome to PF!

Hi missnur! Welcome to PF!

Hint: what conservation equations do you think apply to this problem?

 

[missnur]

Hi. Hmmm..is it the conservative of momentum equation? does it mean that i will have a simultaneous equation?

 

[tiny-tim]

Hi missnur!

Conservation of momentum is a good start.

The question tells you that the collision is perfectly elastic … questions don't say things like that unless they're important … so what does it mean?

 

[missnur]

Thank you tin tim. So when it says its perfectly elastic collision, means there is no loss of kinetic energy, right? So I am suppose to also find the conservative of energy equation?

 

[tiny-tim]

Woohoo! ​

Yes … general principle … in a pure collision (no outside strings or springs etc), momentum is always conserved, and energy usually isn't conserved (unless the question somehow tells you it is)!

( … if aok now, click on "Thread Tools" to mark the thread [SOLVED] … )​