The paradox of lost energy details below?

[chanvick]

Imagine two bodies A & B. they have same mass and same speed, but they are traveling in different direction. the kinetic energies of both the bodies is equal (1/2*mv^2), because they have same speed and mass. now they collide each other. As they have same mass and speed they both stop. now the kinetic energy of both the bodies is zero. but where is the kinetic energy gone...in other words what is it transformed into. but what about law of conservation of energy??

 

[russ_watters]

Welcome to PF!

Some is absorbed due to the physical deformation and some is released as heat and sound.

 

[Doc Al]

but what about law of conservation of energy??

Don't confuse general energy conservation--which includes all forms of energy--with special cases where mechanical energy may be conserved. Total energy is always conserved, but only in special cases will kinetic energy be conserved in a collision, making it a perfectly elastic collision.