Ok, the question is the following:(adsbygoogle = window.adsbygoogle || []).push({});

"In a railroad switchyard, a 56 ton freight car is sent at 7.0 mi/h toward a 31 ton car that is moving in the same direction at 26 mi/h."

- what is the speed of the pair after they couple together?

-what fraction of the initial kinetic energy was lost in the collision?

--> My questions is, to find the momentum, do I need to convert the units to kg? I have seen it in examples where the units are not converted. Does it matter?

--> Also, the fraction of energy lost is expressed as lost energy/initial energy , is that correct?

Thanks

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# Homework Help: Inelastic collision of railcar

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