A kite flies because the wind pushes it

The wind exerts a force on the kite. You can feel this force when you stand with the kite in the wind. The wind pushes the kite (and you). The force can be so strong that you find it difficult to stand still. The wind will blow you away.

The wind also pushes the kite when it flies. It cannot blow the kite away as the kite is tied to the string. But the wind can blow the kite up into the air because the kite is at a slight angle to the wind.

What is happening?

When the kite is flying there are three forces in action. There is the force from the kite string, the force of the wind and the force of gravity.

• The force of the wind pushes the kite upwards and backwards.
• The force of the kite string pushes the kite forwards and downwards.
• The force of gravity pulls the kite straight down to the ground.

The kite stands still in the air when:

• The wind pushes the kite backwards as much as the kite string pushes it forwards
• The wind pushes the kite up as much as gravity and the kite string pull it down.

When the kite stops still in the air, it is said to be in equilibrium.

How does the kite rise into the air?

The kite rises into the air because the wind pushes it upwards more than the kite string and gravity pull it down.

Why does the kite stop rising in the air?

How much the wind pushes the kite up depends on the extent of the kite’s angle to the wind.

When the kite is nearly perpendicular to the wind, the wind pushes it strongly because there is a large area to push. When the kite is nearly parallel to the wind, the wind pushes it weakly because there is less of an exposed area. You can feel this yourself when you walk against the wind with the kite. It is easiest if you turn the kite with its side towards the wind.

As the kite climbs it lies more and more with its side towards the wind. Therefore the wind’s force drops as the kite gets higher and higher. At the exact point where the pushing force of the wind becomes the same as the kite string and gravity, the kite stops climbing.