Question

Explain, why an inflated balloon lying on the surface of a floor moves forward when pierced with a needle.

Answer 1

1. The momentum of the inflated balloon before the piercing is zero.
2. When an inflated balloon is pierced with a pin, the air trapped in it comes out at a certain speed which generates backward force.
3. To conserve this momentum balloon moves in the forward direction.

That is why an inflated balloon lying on the surface of a floor moves forward when pierced with a needle.