Density

One characteristic of matter is DENSITY

Density = mass / volume

Unit: kg / m3 or g / cm3

The density of water is 1000 kg / m3

Or 1 g / cm3

An object will float in a liquid if its density is less than that of the liquid.

Buoyancy-Archimedes Principle

An object immersed in a fluid is buoyed up with a force that is equal to the weight of the displaced fluid.

That’s why you seem to weigh less in a swimming pool that you actually do!

Apparent Weight = Actual Weight – Buoyant Force

In this example, the stone weighs 48 N out of water and 38 N submerged in

water.What was the buoyant force?

How much did the displaced water weigh?

Buoyant Force = Weight of displaced fluid

But buoyancy applies to air as well as water!It is what gives a lifting force to hot air balloons.The weight of the air displaced to make room for the balloon is pushing upward on the balloon!

Archimedes' Principle explains why steel ships float when solid steel spheres do not float. Because of all the air in the hull, the overall

density is less than that of water, therefore, it floats- the buoyant force equals the weight

as the ship floats on the surface of the ocean.

The Titanic, April 15, 1912

The hull was designed to displace 66,000 tons of water.

The gross weight was 46,328 tons.

Therefore, the Titanic had 19,672 tons of extra displacement capacity.

19672 Tons to spareThe Titanic had 16 compartments separated

by 15 watertight bulkheads. If each compartment had the same displacement capacity, then each one would have 4125 tons (66000 / 16).

One flooded compartment: 19,672 – 4125The Titanic is able to stay afloat.Two compartments:Three compartments:Four compartments:Five compartments:

Damage to the hull amounted to only

12 square feet,

but punctured 5 compartments.

The sinking was inevitable.

Fluids in Motion

Fluids include both liquids and gases.

Viscosity: the resistance to flow

Honey is more viscous than water.

Bernoulli’s Principle

The faster a fluid is moving, the lower the pressure within the fluid.

FASTER fluid results in LOWER pressure

SLOWER fluid results in HIGHER pressure

There are MANY applications of Bernoulli’s Principle.

Air Foil

The shape of an airplane wing.

The air moving over the top of the wing reaches the back of the wing at the same time as the air moving along the bottom of the wing. This implies that…..

Air moves faster over the top of the wing. According to Bernoulli’s principle, that results in lower air pressure above the wings than below the wings.

The higher pressure below helps push the wings upward.That’s “lift”.

Atomizer or Paint SprayerA small tube goes down into the

liquid in the container.

Fast moving air moves over the top of the small tube, According the Bernoulli’s principle, this results in LOWER pressure at the top of the tube.

So… the higher pressure at the bottom of the tube will push the fluid up the tube.

Chimney’sThe wind blowing over the top of a chimney results

in a LOWER air pressure at the top of the chimney compared to the bottom of the chimney.

The higher pressure air at the bottom helps push the smoke up and out the chimney.

AneurysmA serious medical condition that can result in death if

not treated promptly.A weakened section of a blood vessel begins to swell

outwards – the vessel widens.This forms an area where the blood slows down:

SLOWER fluid results in HIGHER pressure.This higher pressure makes the vessel swell out even

more…Which makes the pressure go higher…Which makes the vessel swell more…Which…… you get the idea!If not corrected, the vessel will eventually burst. If it is

a major vessel, this a critical situation!