# The Physics of blowing a puff of air

• B
• jhan
In summary: However, a rough approximation could be made by simply assuming that the velocity of the towel at the beginning and end of its flight is the same. This approximation would be valid provided that the air pressure and temperature remain constant. If either of these variables changes, then the velocities of the towel and the surrounding air would no longer be equal and the towel would eventually fall to the ground.
jhan
If we noticed, when we released wind from our mouth with a constant velocity ,Why is the speed of the close part of our mouth is maximum speed and while gradually moving away is also gradually weakened until it is zero?
How it can be resolved using in mathematical expression?

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berkeman
You mean why is a puff of air subject to air resistance?

RobbyQ and russ_watters
jhan said:
Why is the speed of the close part of our mouth is maximum speed and while gradually moving away is also gradually weakened until it is zero?
In the confined space of the small tunnel made by your lips, all of the air is moving rapidly. But when it exits your lips it runs into stationary air and pushes it out of the way. But then this air runs into even more stationary air and pushes it away. Which runs into even more stationary air...etc etc etc. On top of this, the air that's pushed out of the way is replaced by slow moving air coming in from behind, which itself then has to be pushed out of the way by your breath. The end result is that your breath only has a small distance in which it retains any significant velocity.

A similar thing happens with rocket engines. Standing directly underneath a large rocket engine would blow you away immediately (and cook you like a turkey under a blowtorch), but you can stand underneath a rocket flying high overhead and not feel even the slightest breeze.

jhan said:
How it can be resolved using in mathematical expression?
I throw in the towel when it comes to anything beyond basic calculus, of which fluid mechanics definitely is beyond.

Drakkith said:
I throw in the towel when it comes to anything beyond basic calculus, of which fluid mechanics definitely is beyond.
The physics of a towel thrown through the air as it gradually opens up must be quite complicated, I imagine.

Drakkith, berkeman, jbriggs444 and 1 other person

## What is the physics behind blowing a puff of air?

The act of blowing a puff of air involves the movement of air molecules from an area of high pressure to an area of low pressure. When we blow, we increase the pressure in our lungs, forcing the air out through our mouth or nose. This creates a stream of moving air molecules that can be felt as a puff of air.

## Why does blowing on hot food or drinks cool them down?

When we blow on hot food or drinks, we are essentially increasing the rate of heat transfer from the hot object to the surrounding air. This is because the moving air molecules carry away some of the heat energy from the hot object, causing it to cool down faster.

## What factors affect the strength of a puff of air?

The strength of a puff of air is affected by several factors, including the force and speed at which we blow, the size and shape of our mouth, and the density and temperature of the surrounding air. These factors determine the amount of air molecules that are moved and the force with which they are moved.

## Can blowing a puff of air cause changes in air pressure?

Yes, blowing a puff of air can cause changes in air pressure. When we blow, we are essentially creating a temporary increase in air pressure in our mouth, which then decreases as the air moves out. This can be demonstrated by blowing up a balloon or blowing out a candle.

## How is the physics of blowing a puff of air related to other scientific concepts?

The physics of blowing a puff of air is related to several other scientific concepts, such as fluid dynamics, thermodynamics, and aerodynamics. It also involves the principles of force, pressure, and energy transfer. Understanding the physics behind blowing a puff of air can help us better understand these related concepts and their applications in various fields.

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