Forces In Fluids

Fluids include: Liquids and Gases Fluid – any material that can flow and takes the shape of its container Fluids include: Liquids and Gases

Flow happens when particles move easily past each other

Air pressure and water pressure? All fluids exert pressure

Pressure – amount of force exerted on a given area

Force Pressure = Area Pressure is measured in: pascals (Pa) Equation: 1 Pa is the force of 1 N exerted over an area of 1 square meter

Force Area Pressure = What is the pressure exerted by a book that has an area of 0.2 m² and a weight of 10 N?

Find the pressure exerted by a 3000 N crate that has an area of 2 m². Force Area Pressure = Find the pressure exerted by a 3000 N crate that has an area of 2 m².

Force Area Pressure = Find the weight of a rock that has an area of 10 m² and that exerts a pressure of 250 Pa.

Fluids exert pressure evenly in all directions When you blow a bubble, you blow in only one direction. So why does the bubble get rounder instead of longer as you blow? Fluids exert pressure evenly in all directions Bubbles: expand in all directions to make a sphere

layer of nitrogen, oxygen, and other gases surrounding the earth Atmosphere layer of nitrogen, oxygen, and other gases surrounding the earth What keeps those gases from floating away?

Atmospheric pressure pressure caused by the weight of the atmosphere

Atmospheric pressure is exerted on everything on Earth At sea level, you have a weight of about 10 N (2lbs) pushing on every cm2 of your body Why don’t you feel it? Fluids inside us push back

Pressure inside = Pressure outside

Atmosphere stretches about 150 km above the Earth’s surface Atmosphere stretches about 150 km above the Earth’s surface. However, 80% of the atmospheric gases are found in the 10 km

Differences in Atmospheric Pressure At sea level – full weight of atmosphere (101 kPa) is exerted on you

Differences in Atmospheric Pressure La Paz, Bolivia (world’s highest capital city at 4000 m) has atmospheric pressure of 51 kPa

Differences in Atmospheric Pressure Mt. Everest is the highest point in the world and has an atmospheric pressure of 33 kPa

Differences in Atmospheric Pressure Atmospheric pressure at 12000 m is about 20 kPa. Airplane cabins must be pressurized for passenger safety

Differences in Atmospheric Pressure At 150,000 m above sea level, atmospheric pressure is almost 0 Pa. Major protection is needed

As you increase in altitude, what happens to the atmospheric pressure? DECREASES

Altitude Sickness? Exposure to low oxygen levels from 2,400 m above sea level

Water Pressure

Water pressure increases as depth increases

Water is about 1,000 times more dense than air   Water exerts more pressure than air

If you climb a 10 m tree, the decrease in pressure is too low to notice. If you dive 10 m below water, pressure almost doubles

Differences in Water Pressure At 10 meters below the surface, pressure is about 100 kPa

Differences in Water Pressure At 500 m below the surface, pressure is about 5,000 kPa. Divers have to wear special suits to survive the pressure.

Differences in Water Pressure The wreck of the Titanic is 3,660 m below. Water pressure is 36,600 kPa

Differences in Water Pressure Viperfish live 8,000 m below and no fish are found lower. Pressure is 80,000 kPa

Differences in Water Pressure In 1960, the Trieste descended to the deepest part of the ocean (11,000 meters) where water pressure is 110,000 kPa

As you move deeper, the pressure increases

Diving sickness Increasing pressure to the body too quickly nitrogen gas bubbles are released into the bloodstream and tissues, which can cause numbness, dizziness, weakness, nausea, pain, headaches, itching, and visual disturbances.

Fluids flow from areas of high pressure to low pressure

You can see this in… Soda Can Breathing Tornadoes

 gas inside the can is more pressurized than gas outside so when opened, gases will escape

Inhale diaphragm contracts making lung space increase.

Inhale Air pressure outside is higher so it flows into lungs

Exhale diaphragm relaxes making lung space decrease

Exhale Air pressure inside lungs is greater so it flows outside body

Tornadoes Air pressure inside tornado is low while air pressure outside is high. This causes air and other objects in its path to be sucked into the tornado

Mythbusters Pressure Differential http://www.youtube.com/watch?v=OPKP8qweGb8