(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..

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

**Physics Forums | Science Articles, Homework Help, Discussion**