Speed and Mechanical Energy Lost in Railroad Car Collision

AI Thread Summary
In a railroad car collision scenario, a single car of mass 2.49 x 10^4 kg traveling at 3.89 m/s collides with three coupled cars, each of the same mass moving at 1.95 m/s. The conservation of momentum is applied to determine the final speed of the four coupled cars after the collision. The equation used is 2.49e4 * 3.89 + 3*2.49e4 * 1.95 = 4*4.29e4 * V, where V represents the final speed. After calculating the final speed, the initial and final kinetic energies can be compared to determine the mechanical energy lost during the collision. This analysis highlights the principles of momentum conservation and energy loss in inelastic collisions.
TrippingBilly
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A railroad car of mass 2.49 104 kg, is moving with a speed of 3.89 m/s. It collides and couples with three other coupled railroad cars, each of the same mass as the single car and moving in the same direction with an initial speed of 1.95 m/s.
(a) What is the speed of the four cars after the collision?
(b) How much mechanical energy is lost in the collision?

Sorry, but I have no idea about this problem :(
 
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Hint: What is conserved in any collision?
 
Momentum, so...

2.49e4 * 3.89 + 3*2.49e4 *1.95 = 4*4.29e4 * V

?
 
TrippingBilly said:
Momentum, so...

2.49e4 * 3.89 + 3*2.49e4 *1.95 = 4*4.29e4 * V
Right. Looks good, except for a typo. Once you solve for the final speed, you can figure out the initial and final kinetic energies and compare them.
 

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