## physics giancoli 6th edition

**Two train cars A and B have different masses:m(A)=15,000kg,m(B)=13,000kg on the same track..?**

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(Physics Giancoli 6th edition 2004, chapter 7, similar to example 7-3 using conservation of momentum)
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In the real world the collision is inelastic, that is the kinetic energy before collision is not equal to the kinetic energy after collision. Use the data in “PART 1″ to calculate the difference in kinetic energy before and after the collision.

Thanks guys!

Let us thank the principle of conservation of momentum. Before collision, the total momentum was

15000*28+13000*0 = 420000 kgm/s

After collision let the coupled move with a velocity v. Then the final momentum is 28000*v

By the conservation of momentum, 28000 v = 420000

So v = 15 m/s

Let us compute the KE before collision and after collision. The familiar expression 1/2 m v^2 is to be used.

1/2 {15000*784+13000*0} = 5880000 J this is the KE before collision.

After collision 1/2 * 28000*225 = 3150000 J

So certainly there seems a loss of KE. It is 5880000–3150000 = 2730000 J

**Giancoli solutions: Chapter 5 Problem 2, 6th Edition, or Chapter 5 Problem 1, 5th Edition**