Physics and conservation of energy?

Question

Two railroad cars, each of mass 6520 kg and traveling 95 km/h, collide head-on and come to rest. How much thermal energy is produced in this collision?

Answer 1

1/2*m*v sq + 1/2*m*v sq =heat evolved(assuming whole mechanical energy is converting into thermal energy)

Answer 2

There are two type of collision In the Universe. One is called elastic the other is called inelastic.
Except for one case all collision in the Universe are not perfectly elastic.
When two masses approach each other to collide,at the collsion frame of reference the following happens;
The Energy of motion add up to a total energy.
The equivalent collision velocity in the case of the rairoad cars is the square root of total Energy /mass of railroad car .
The car energy = 6520 x(95000/3600)^2
The collison velocity =square root of 2 x 26.3888m/sec
which is 37.31 meters per sec or 134.3 km /hr This is the velocity that Einstein alluded to about addition of velocity of 2 moving bodies.The collison velocity is always less than the the sum of the relative velocities.
At that point a force is born between the two railroad cars.
since the collison is non elastic ,the forces produced is that of deformation and mass is lost in terms of heat radiation .
To calculate the force acceleration need to be known.
The heat lost at the collision depends on the resistivity of the materials which were deformed.
So the thermal energy lost is equal the the total collision energy minus the energy that caused the deformation.
so in inelastic collision the total energy is not conserved nor is the momentum conserved because heat energy is lost to the surrounding.

Answer 3

Clearly a great deal of energy will be convereted from kinetic energy to other forms in this tragedy. It is impossible to tell how much of that energy will be thermal energy. Some of the energy will be sound energy (a very loud crash will ensue). Most of the energy will be mechanical energy which will go into deforming the components. Some of the energy may go into thermal energy, but it strikes me that actually this will be a very low portion of the total energy. (Very little heating up actually occurs during such a collision.)

Answer 4

The answer -- none!

It took thermal energy to accellerate the mass, and it will all be dissipated when the mass comes to rest. So, because of conservation of energy, none is produced. Unless, of course, the trains are carrying a fusion bomb or two.