Why Don't Gas Particles Get Pulled Towards Earth If Gravity is Constant?

[rishch]

Can three concurrent, non co planar forces be in equilibrium? also,

If g is a constant then why don't gas particles get accelerated towards the Earth?

 

[mikeph]

I would say no, but it's the sort of question that demands a proof accompanying the answer... I would suggest that three vectors which are not all coplanar must also be orthogonal, and therefore there is no way that they can sum to zero. To answer your second question, gas particles are subject to the force of gravity but there are other forces which stop all the molecules from falling onto the surface (collisions).

 

[torquil]

I would say no, but it's the sort of question that demands a proof accompanying the answer... I would suggest that three vectors which are not all coplanar must also be orthogonal, and therefore there is no way that they can sum to zero.

They don't have to be orthogonal. But as you say, they cannot sum to zero. If they did, they would be linearly dependent. And then, any linear combination of the three could be reduced to a linear combination of two of them. Therefore, they would only span a plane, or less, which is against the assumption of not being co-planar.

 

[mikeph]

A much better way of saying it! Thanks, orthogonal was the wrong word.

 

[pmacias]

I can explain that gas particles do experience the force of gravity from the Earth, just like all other objects on the planet. However, the reason they do not get pulled towards the Earth is due to the balance of other forces acting on them.

Gas particles are in constant motion due to their high kinetic energy, and this motion creates a force known as pressure. The pressure of the gas particles pushing against each other and the walls of their container creates an outward force that counteracts the force of gravity pulling them towards the Earth. This results in a state of equilibrium where the forces are balanced and the gas particles remain in their current state.

In addition, the Earth's atmosphere is also constantly in motion due to factors such as wind and convection currents. This creates a turbulent environment where gas particles are constantly moving and colliding with each other, further preventing them from being pulled towards the Earth.

As for the second question, it is possible for three concurrent, non co-planar forces to be in equilibrium. In this scenario, the forces would have to be carefully balanced and their directions and magnitudes would have to be precisely calculated. This is known as the principle of moments, where the sum of the clockwise moments must equal the sum of the counterclockwise moments for equilibrium to occur. This principle applies to many real-life situations, such as balancing a see-saw or a bridge.