As the rubber sheet is pulled down the volume of the jar increases, the pressure therefore decreases and air is drawn in through the glass tube inflating the balloons, which represent the lungs.

What happens to the balloons when the rubber sheeting is pulled upward?

When the rubber sheet is pushed upwards into a dome shape, the balloons become deflated. This is because the air volume inside the bell jar decreases, thus increasing the air pressure. As a result, the volume of the balloons decreases and the pressure increases.

Why does air rush in when the rubber sheet is pulled down?

1. When the rubber sheet is pulled down, the balloon gets filled with air because the cavity increases and air rushes in. This is exactly what happens during inhalation. The diaphragm contracts and the air rushes into the lungs.