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

A 1200-kg car traveling initially with a speed of 25.0 m/s in an easterly direction crashes into the rear end of a 9000-kg truck moving in the same direction at 20.0 m/s. The velocity of the car right after the collision is 18.0 m/s to the east. (a) What is the velocity of the truck right after the collision?(b) How much mechanical energy is lost in the collision? Account for this loss of energy.

It's sub-question (b) that's causing trouble.

2. Relevant equations

[tex]m_1 v_{1i} + m_2 v_{2i} = m_1 v_{1f} + m_2 v_{2f}[/tex]

[tex]\frac{1}{2}m_1 v_{1f}^2 + \frac{1}{2} m_2 v_{2f}^2 - (\frac{1}{2} m_1 v_{1i}^2 + \frac{1}{2} m_2 v_{2i}^2) = - \Delta KE[/tex]

3. The attempt at a solution

I did part (a) fine and substituted those values into the second equation above but the answer was not the same as in the book. What could possibly be wrong?

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# Loss of Mechanical Energy after Collision

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