total momentum is not always conserved .true or false.if true explain if false explain

Question

anonymous · Answer

is conserved ,when no force act on system that you define .maybe you define a system that force act on it so  total momentum is not conserved for more information see Wikipedia

anonymous · Answer

can u please b more precise as a physisit

anonymous · Answer

suppose this figure :|dw:1329061665329:dw|
momentum will not conserve ,if you take body(just body) for system ,hence friction act on system,now assume body+ground for system here momentum will conserve hence all of force that act ,are interior