0Lets say you are standing on a frictionless platform of ice. And you are holding a 10kg bag .
You cannot walk on this platform as there is no frction , you will slide.
Now lets say you want to move in right direction. What will you do.?
Just throw that bag in left direction, you will get some velocity in opposite direction by the law of conservation of momentum.
NOTE HERE IS : there is no friction or any other non conservative force . Its an assumption
