Please could you each describe the limits of the system that you are considering.dmrcycle wrote: ↑23 Sep 2022, 5:17pmNo absolutely not the case, thats conservation of energy. Momentum is only conserved if there are no other forces acting. Newton stated that is the case.
See
http://teacher.pas.rochester.edu/PHY_LA ... _Laws.html
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Friction between moving bodies and their surroundings means there is an external force acting on them, so that conservation of momentum is not applicable.
Confusion between conservation of momentum and conservation of energy is what is the issue here. I can appreciate it might have been some time from school level physics but the information can be looked up. In a collision energy is conserved momentum is not unless its a perfect situation (similar to two billiard balls). If there is friction, deformation, heat, sound etc then conservation of momentum does not apply. The momentum (mass x velocity) is not the same after the interaction. Think about it, otherwise we would all be bumping around never stopping transferring 100% of our momentum between things we touch. Nothing slowing down. When energy is absorbed and converted from kinetic energy to heat (aka braking) it cant be conserved as you slow down and have less momentum. This is basic school level stuff.
Thanks
Jonathan