Answer:
the filling stops when the pressure of the pump equals the pressure of the interior air plus the pressure of the walls.
Explanation:
This exercise asks to describe the inflation situation of a spherical fultball.
Initially the balloon is deflated, therefore the internal pressure is equal to the pressure of the air outside, atmospheric pressure, when it begins to inflate the balloon with a pump this creates a pressure in the inlet valve and as it is greater than the pressure inside, the air enters it, this is repeated in each filling cycle, manual pump.
When the ball is full we have two forces, the one created by the external walls and the one aired by the pressure of the pump, these forces are directed towards the inside, but the air molecules exert a pressure towards the outside, which translates into a force. When these two forces are equal, the pump is no longer able to continue introducing air into the balloon.
Consequently the filling stops when the pressure of the pump equals the pressure of the interior air plus the pressure of the walls.
