If evrything is pulled down by gravity then how come smoke rises up?

Answer 1

The particles making up the smoke are lighter than the surrounding air. The heavier air above it will tend to fall through the smoke making it rise and dissipate.

Answer 2

The particles in the smoke ARE being pulled down by gravity. Even though they may be microscopic, they still have weight. Weight is the effectof gravity. However, hot air will rise. The thermal energy causes air molecules to move faster than colder ones, and so they have more collisions with each other and also move further. The net effect of this is that air which has been heated rises. Smoke particles in this warm air (can't have smoke without fire, can't have fire without heat!) are carried upwards by the movement of the warm air molecules. So they have an upward force acting on them as well as a downward force due to gravity. The upward force is generally greater (gravity on particles is very weak) so smoke rises.

You were right when you said everything is pulled down, but you need to remember that there are also forces acting upwards!

Answer 3

The answers that say that instead of the smoke rising the air is pulled down are really the best way to look at the problem. Both the smoke and air are pulled down by gravity it is just that the smoke is pulled down less. This is the way a real nerd would look at the problem. (;>)

Answer 4

The force generated by gravity is so tiny that it can be negated or overcome very easily. If you look the mass of the earth and the gravitational force it generates you'll realise how small this force is when it can be overcome by throwing a ball in the air for example. The force which moves the ball upwards is eventually equalled and overcome by the earths gravity (which accelerates at 9.8m/s/s) and falls to the ground. The same happens for smoke, the force moving it away from the earth is air pressure - heat rises. eventually as the gas within the smoke cools and becomes more dense that upward force weakens and the soot and heavy particles within the smoke fall to earth due to gravity!

Answer 5

Smoke does not escape the earth's atmosphere, it is still bound by gravity, but because it is not bound to the same extent as it's relative surroundings such as concrete, paper, water etc. it appears to defy gravity. Think of a bonfire, and you'll see that the smoke only rises for a few hundred feet before it becomes 'heavy' again because of humidity, colder air and so forth, and either disperses into smaller particles or sinks to the ground - you can see the effect with ashes too, like 'chunky' smoke.

Answer 6

Everything is pulled down - but some things are pulled down more than others...

If you fill a plastic bottle with air, and put the lid on, then push it to the bottom of the bath, gravity pulls it towards the centre of the earth - but gravity *also* pulls at the water around it - as the water is pulled down, it displaces the air-filled bottle, which rises. Heavier thing goes down, lighter thing gets pushed up.

Nature abhors a vacuum - but even more so, she abhors two things being in the same place at the same time.

Helen

Answer 7

Smoke is usually (mainly) fine particles of carbon - oxidised - whatever the substance was being burned - obviously heavier than air. Certainly you cannot say that smoke is heavier than gravity - gravity doesn't have a weight.

Because the particles are so fine they are suspended in the hot air (that is necessarily produced because of the burning producing the smoke) and hot air (gas) rises carrying the smoke (carbon particles) because the hot air is not as heavy as the surrounding cold air.

As the air cools and dissipates the carbon - smoke particles will eventually fall back to Earth because of gravity.

Answer 8

Because the are hot and get carried up with the rising thermal.

The smoke eventually does fall to earth but it is dispersed over a vast area that you would be able to detect.

The earths gravity is powerful enough to keep most things stuck to its surface which is nothing more than fine particles of dust and other materials that have been made from it.

A recent programme on TV showed that the earth is nothing more than a giant ball of dust particles in varying sizes that have been melted and reacted with to form all the elements we see around us!

Answer 9

Smoke only rises if the gases contained in it are hotter than the surrounding air. It should be noted that smog was caused by the particles in the smoke being trapped below a warm layer. Thus smoke only rises when hotter than the surrounding air, watch the smoke from a bonfire of leaves and note that mostly the smoke will follow the ground as it has been cooled as it clears the fire.

Answer 10

The heat from a fire causes hot air above the fire to rise due to convection currents and decrease in density of the air.
This causes the smoke to rise with it.
Smoke contains solid particles of carbon (soot) which are normally heavier than air and, as the rising air and smoke cool down further away from the fire, the smoke particles will eventually fall back to earth.

Answer 11

Gravity is just one of many forces that act on bodies everywhere, every second of the day. The moon is acted on by earths gravity, but it doesn't fall into the earth, and what abouts planes?

It is all about forces, of which gravity is one. As already noted above, there is an upward force which acts on smoke due to it having heat. This is greater than the force of gravity pulling the smoke particles down. hence smoke rises.

When you consider a plane, you look a the lift and weight forces. The plane rises because lift exceeds the weight, due to pressure differentials across the wings.