(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Two railroad cars, each with a mass of 7,000kg and traveling at 90 km/h collide head on and come to rest. How much mechanical energy is lost in this collision?

2. Relevant equations

[tex]KE=\frac{1}{2}mv^2[/tex]

3. The attempt at a solution

[tex]KE=\frac{1}{2}(7000)(90)^2=2.835*10^7[/tex]

Mechanical energy = KE+PE. PE = 0.

Energy lost = 2KE or [tex]5.67*10^7[/tex]

Book answer is [tex]4*10^6[/tex]

Where am I going wrong? Thanks..

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# Energy Loss in Head on Collision of Two Cars w/Same Speed and Mass

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