Fluid: a substance that has definite mass but not definite shape.

Ex: gases and liquids Density: mass/volume

ρ Units: ρ water = 1 g / cm³ =

 __________kg/m² = __________Kg/L

 Weight of a Fluid – force gravity exerts on a fluid = mg

Equation:

Specific Gravity - density of a fluid compared to the density of water.

Specific Gravity - comparison of the density of a substance with the density of water

Specific Gravity	=

Alcohol or lead, which has a specific gravity of 11?

Pressure = F/A

N/m² or Pascal

Pressure under a Liquid 

P₀ – pressure above liquid

(Density in liq. depends only on h)

(Density depends only on h)

P₀ – pressure above liquid

(usually atmospheric pressure)

at sea level

1 atm = 1.013 x 10⁵ N/m²

Pascal’s Principle

If a force is applied on one place in an enclosed liquid the pressure increases everywhere else in the liquid.

Giancoli p. 281) 14, 16 - 17

density of water = 1000 kg/m³

Buoyancy

"Archimedes Principle"

Why do some substances float in a liquid and some sink?

Objects that are less dense than the liquid sink.

The buoyancy force produced by a liquid is equal to the weight of the volume displaced

F_B= Weight of fluid displaced= Weight of fluid displaced

F_B = mg

Buoyancy force = submerged weight  

(r_fluid)(V_submerged)g = mg

(r_fluid)(V_submerged) = m_object

OR

Displ. Mass_liq. = Mass_object

Gauge Pressure - fluid pressure w/o atmospheric pressure

Absolute Pressure - fluid pressure with atmospheric pressure

F_b = Weight_air - Weight_liq

Apparent Mass or Weight

- mass or weight in fluid

 V of liquid displaced

= V of object submerged

Density / Part Submerged

Partially Submerged /
Density and SG

©Tony Mangiacapre., St. Mary's H.S., Manhasset, NY
All Rights Reserved [Home] Established 1995