unde what conditions does conservation of momentum apply? compare these conditions to the conditions needed for energy conservation. are there any similarities? differences?

Question

amistre64 · Answer

i believe CoM applies to both elastic and inelastic conditions.; its Kinetic energy that differes between the two.

anonymous · Answer

Conservation of linear momentum is a result of symmetry with respect to space. In absence of any external forces, the configuration of a particular system will not change if translated in space to some other location, and that leads to conservation of linear momentum. Likewise isotropy in space , i.e. configuration of a system does not change under rotation in absence of external forces leads to conservation of angular momentum. SO conservation of momentum is an consequence of spatial symmetry. So the conditions needed are homogeniety and isotropy of spacfe together with absence of any external forces.

Whereas conservation of energy is based on homogeneity of time. If the system property remains the same at different instances of time, energy will be conserved. So even if in presence of external forces energy will be conserved only if the forces are not varying in time.