Conservation of energy/momentum

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SUMMARY

The discussion focuses on a railroad accident involving a boxcar weighing 200 kN and a stationary caboose weighing 400 kN. The initial kinetic energy of the boxcar is calculated to be 900,000 J, and the initial momentum is 600,000 kg m/s. The final momentum after the collision must equal the initial momentum, leading to a combined mass of 61,200 kg for the boxcar and caboose. The reduction in kinetic energy during the collision is identified as energy transferred to other forms, primarily heat and sound.

PREREQUISITES
  • Understanding of kinetic energy calculations using the formula KE = 1/2 m v^2
  • Knowledge of momentum conservation principles (P = mv)
  • Basic physics concepts related to energy transfer during collisions
  • Familiarity with unit conversions between kilonewtons and kilograms
NEXT STEPS
  • Calculate the final velocity of the combined boxcar and caboose after the collision
  • Determine the total energy loss during the collision and its forms
  • Explore the principles of inelastic collisions in physics
  • Investigate real-world applications of momentum conservation in engineering
USEFUL FOR

Physics students, educators, and engineers interested in understanding energy transfer and momentum conservation in collision scenarios.

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Homework Statement


In a railroad accident, a boxcar weighing 200 kN and traveling at 3.00 m/s on a horizontal track slams into a stationary caboose weighing 400 kN. The collision connects the caboose to the boxcar. How much energy is transferred from kinetic energy to other forms of energy in the collision?


Homework Equations


KE= 1/2 m v^2
P= mv


The Attempt at a Solution


KE initial= 1/2 (200000) (3)^2
=900000 J
P initial= 200000 (3)
=600000 kg m/s

I have no idea where to go from here
 
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Point 1: The mass of the boxcar is only about 20000 kg, not 200000 kg. Maybe 20400 kg.
Point 2: The final momentum will NECESSARILY equal the initial momentum, and the final mass is necessarily 61200 kg, so the final velocity of the stuck-together mess is easy to find.
Point 3: Once you have the final velocity, you can find the reduction in kinetic energy -- all of the reduction is "transferred to other forms of energy" - mainly heat, but possibly sound, etc.
 

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