Why does air leave the tire when valve is opened?

When you open the valve on a tire, the air inside the tire is at a higher pressure than the air outside the tire. This difference in pressure causes the air to flow out of the tire through the valve.

The amount of air that flows out of the tire depends on the difference in pressure between the air inside and outside the tire. The greater the difference in pressure, the more air will flow out of the tire.

This is why it is important to keep your tires properly inflated. If your tires are underinflated, the difference in pressure between the air inside and outside the tire will be greater and more air will flow out of the tire when you open the valve. This can cause your tires to go flat.