P11.3 Atmospheric pressure

Question 1

What is atmospheric pressure caused by?

Answer 1

Air molecules colliding with surfaces - each impact exerts a tiny force on a surface - number of molecules that collide with the surface each second is very large

Question 2

Why does the density of the atmosphere decrease with increasing height above the ground?

Answer 2

This is because the weight of air pressing down on a horizontal surface at any altitude decrease with altitude - so therefore there is fewer impacts per second at a higher altitude

Question 3

Why does a rubber suction cap pressed onto a wall tile stay on the tile?

Answer 3

Because atmospheric pressure acts on the outside of the cap but not on the inside between the cap and the wall

Question 4

What is the formula to find the pressure at sea level?

Answer 4

Pressure p = height, h x density, p x gravity, g

Question 5

What is the force on a flat object due to?

Answer 5

A pressure difference = the pressure difference x area of the flat surface