P11 Force And Pressure Flashcards
Pressure =
Force / area
Unit of pressure
Pascal (Pa)
1 Pa =
1 N/m^2
Pressure in a liquid =
Height x density x gravitational field strength
Pressure at sea level =
Height x density x gravity
Unit for density
Kg/m^3
Unit for gravity
N/Kg
Atmospheric pressure is due to…
Air molecules colliding with surfaces
Why does atmospheric pressure decrease with altitude?
The air is less dense so there are fewer molecules per cubic metre and therefore fewer impacts per second. The weight of air above any given altitude exerts pressure on the air below. At increased altitude, there is less weight of air above so atmospheric pressure is lower.
The force on a flat object due to pressure difference =
The pressure difference x the area of the flat surface
The more an object is lowered into the water,
The bigger the volume of water displaced, and the bigger the upthrust
When an object is fully immersed,
The volume of water displaced is equal to the volume of the object
An object sinks if
Its weight is greater than the upthrust on it when it is fully immersed
An object floats if its density is
Less than that of the fluid
