Answer:
This is because of Newton's third Law of motion :
For every action there is equal and opposite reaction .
Step-by-step explanation:
When air is squeezed out from the balloon , the potential energy (Shape of balloon) is converted into Kinetic energy. This kinetic energy is possessed by fast moving air particles coming out from balloon.These air particles are pushed backward,so according to Newtons third law , the balloon should fly upward.
