# Velocity of 2 objects

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.

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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
Homework Helper
Welcome to PF!

Hi missnur! Welcome to PF! Hint: what conservation equations do you think apply to this problem? Hi. Hmmm..is it the conservative of momentum equation? does it mean that i will have a simultaneous equation?

tiny-tim
Homework Helper
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? Thank you tin tim. So when it says its perfectly elastic collision, means there is no loss of kinetic energy, right? So Im 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] … )