P1.9 Atmospheric Pressure

• Does atmospheric pressure increase or decrease with altitude?

  Atmospheric pressure decreases with altitude (as you get higher up)
• What does altitude mean?

  Altitude is the height above the ground. So a higher altitude means higher up in the atmosphere.
• What is the atmosphere?


  The atmosphere is the layer of gas that surrounds the earth.
• Why does atmospheric pressure decrease with altitude?

  The pulling force from the gravitational field of earth becomes weaker as altitude increases, so gas particles spread further apart, and the atmosphere becomes less dense.
• What is atmospheric pressure?

  Atmospheric pressure is the total force of all the air particles constantly colliding with everything, from all sides.
• What are the main two gases in the atmosphere?

  Nitrogen (78%) and oxygen (21%).
• Atmospheric pressure is lower at a higher elevation. At higher elevation (altitude) the gas particles are more spread out, so they generate less pressure. 
• The atmosphere on earth is made up of countless gas particles, all flying about in random directions. The atmosphere on earth is made up of countless gas particles, all flying about in random directions. In reality, this means any object on earth is being constantly hit, from all sides, by a huge number of tiny forces. This is what 'atmospheric pressure' refers to - the total force of all the air particles constantly colliding with everything, from all sides.
• There is greater atmospheric pressure at sea level than at higher elevation. Why is this?

  1. The air is more dense at sea level.
  2. There are more gas particles at sea level to collide with objects.