yes
the air is thinner
yes because the higher you go in altitude the air gets thinner
Better fuel economy. The air is thinner at higher altitudes.
It is not so much as the composition that is important, it is that at higher altitudes there is less air. Air is about 20% oxygen, but the higher up you go in altitude, the thinner air will have less oxygen. That's what makes breathing more difficult at higher altitudes.
As at higher altitudes the density of air decreases, which means that air is thinner. As a result golf ball travels farther at a higher altitude because of decreased drag on the ball.
The density of air decreases at higher altitudes.
because there is low pressure at higher altitudes
There is less oxygen in the air at higher altitudes. The atmosphere is held in place by the force of gravity, and it is thicker at the bottom, and gradually becomes thinner the higher you go. If you get high enough, the air runs out completely and you are then in outer space. Better wear your spacesuit!
The higher you go the thinner the air is, and less resistance is offered by it. Thus, airplanes fly at high altitudes because the fuel consumption is lower.
At higher altitudes, the air becomes thinner. Since there are fewer molecules, the air has a lower total kinetic energy, which means the temperature is lower.
The simple answer is oxygen starvation. The best athletes train at the higher altitudes because that is where the air is thinner. This forces the human body to work harder, just to expend equivalent energy. People that climb Mt. Everest often suffer from 'altitude sickness' due their lack of conditioning.
This is mainly because the air/fuel mixture is not set for the higher altitudes. The lower atmospheric pressure at higher elevations means the engine will operate leaner then the ideal air/fuel mixture. If you set a vehicle to operate at only high altitudes then it would run to rich and have less power once you left the mountains. This overly lean condition is also why an engine will overheat more easily at high altitudes. The thinner amount of oxygen of higher altitudes also has a very minor role in having less power.