Why does a flag flutter, when strong winds are blowing on a certain day?

You see that leaves of trees, banners or flags flutter when the wind is blowing. Why is it so?

Why does a balloon inflate when air is blown into it ?

Why does a salt disappear when dissolved in water ?

Why do the window panes break and fall out wards and the curtains over the open windows move out of the room and not into the room when strong winds blow along the sides of a building?

Why does a gun recoil When a bullet is fired ?

A sound source and a listener are both at rest on the earth , but a strong wind is blowing from the source towards the listener. Is there a Doppler effect ? Why or why not ?

Why does the sky appear blue on a clear day ?

Flags flutter in breeze. Why?

When you are standstill holding a flag, the flag flutters in the direction of wind. When you start running the direction of fluttering of the flag changes to the direction of the wind relative to you. In all case a flag flutters in the direction of the wind relative to the flag. Holding a flag, when you run at 8 m/s due cast, the flag flutters in the north and when you run at 2m/s due south, the flag flutters in the northeast. If the wind velocity is unifoem and remain constant, find the wind velocity.