﻿    What is density?

Density Units -  kg/m3 Giancoli - p. 281) 2 - 4 densities found on p. 256

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. F2 = A2 F1 A1

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 FB= Weight of fluid displaced= Weight of fluid displaced

FB = mg

Buoyancy force = submerged weight

(rfluid)(Vsubmerged)g = mg

(rfluid)(Vsubmerged) = mobject

OR

Displ. Massliq. = Massobject Gauge Pressure - fluid pressure w/o atmospheric pressure

Absolute Pressure - fluid pressure with atmospheric pressure Fb = Weightair - Weightliq

Apparent Mass or Weight

- mass or weight in fluid

 mg - mg = rVg weight in air (apparent mass or weight) Mass of liquid displaced

V of liquid displaced

= V of object submerged Density / Part Submerged

 Density Part Submerged 800 kg/m3 8/10 submerged 250 kg/m3 1/4 submerged SG = .75 3/5 submerged 125 kg/m3 1/8 submerged Density? Partially Submerged /
Density and SG

 Apparent Mass or Weight in Liquid = SG Mass or Weight in Air    ©Tony Mangiacapre., St. Mary's H.S., Manhasset, NY