Elastic Collision, this happens only when the questions states correct?

[libraryismyhome]

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Even if there is a circumstance which both objects had velocity after collision (mv1+mv2 = mv3+mv4), unless the question states that it is elastic, it is never elastic correct?

 

[Rabolisk]

You can't assume that something isn't elastic. Elastic means conservation of kinetic energies for the system. You have to evaluate that yourself. But your case seems ambiguous. Are you saying that each object had same velocity after the collision as before the collision? Also, note that momentum is a vector while kinetic energy is not. It's hard for me to judge whether your case is elastic or not without knowing more.

 

[flodhi1]

Even if there is a circumstance which both objects had velocity after collision (mv1+mv2 = mv3+mv4), unless the question states that it is elastic, it is never elastic correct?

You will have to analyze other evidence provided in the passage. You can never make assumptions on the elasticity or non-elasticity of a collision. Either way both cases momentum is conserved only difference is the elastic has full conservation of Kinetic energy. Can you state the whole passage and than maybe I can help you ?