Bellwork 44 1 What is air pressure 2

Bellwork 4/4 1. What is air pressure? 2. Is air pressure being exerted on you right now? How do you know?

What is air pressure? Can we feel air pressure? How do we measure air pressure? How do we know it exists?

Quick Demo Stations: • Visit each table and try the short activity • Follow directions, don’t make a mess • Be curious

Atmospheric pressure v. Force exerted by the weight of the air above v. Weight of the air at sea level • 1 kilogram per square centimeter (also called “ 1 atmosphere”) v. Decreases with increasing altitude v. Units of measurement • Millibar (mb) • 1 mb = 100 Pascals= 1 Newton/m 2

Wind v. Horizontal movement of air • Moves from High Pressure Areas to Low Pressure Areas • Pressure differences are a result of the uneven heating of earth. • Solar radiation is the ultimate energy source for wind

3 Factors that Affect Wind 1. Pressure gradient force • Pressure gradient = pressure change over distance • The greater the pressure difference, the greater the wind • Isobars: lines of equal air pressure • Measured in millibars Bottle/Balloon Demo

Closer the isobars are together, the faster the wind speed Faster winds = lower pressure Bernoulli’s principle (Hair Dryer Demo)

Drawing Isobars

Wind Joke!

3 Factors that Affect Wind 2. Coriolis Effect • Apparent deflection in the wind direction due to Earth's rotation • Deflection is the right in the Northern Hemisphere and to the left in the Southern Hemisphere

The Coriolis effect

3 Factors that Affect Wind 3. Friction • Only important near the Earth’s surface— “Upper Air Winds” are not affected by friction. • Acts to slow the air's movement

The geostrophic wind

Practice: Pressure Gradient: Coriolis:

Million Dollar Bet 1) Take a small piece of the paper and make it into a small ball about the size of a large pea. 2) Set the bottle down on its side laying flat on a counter or table. 3) Place the paper ball in the mouth of the bottle. 4) Try to blow the ball inside the bottle. What happens? 5) Bet your friends a million dollars if they can do it! (Not really. )

Mesh Magic! (no…it’s science) 1. Take the piece of mesh and cover the mouth of a bottle. Secure tightly with a rubber band. 2. Fill the bottle up with water. 3. Invert the bottle over a sink. What happens?

Ping Pong Ball Bottle 1. Fill the bottle up with water. 2. Place the ping pong ball over the mouth of the bottle. 3. With one finger on the ping pong ball, invert the bottle over a sink. Make sure no water is leaking from the mouth of the bottle. 4. Remove your finger from the ping pong ball. What happens?

Funnel Fiasco 1. Use a large piece of paper to create a funnel. Make sure the small opening is small enough that the ping pong ball will not fall through. 2. Tape the paper in place. 3. Place the ping pong ball in the funnel. Hold the funnel completely vertically. Try to blow the ping pong ball out of the funnel. What happens? 4. Make a smaller funnel and try the same thing. What happens?

Skewered Bottle 1. Fill a plastic cup with water. Stick a straw in the cup. Cover the opening of the straw with your finger. Lift the straw up with your finger still covering the opening. What happens? 2. Now, stick the skewer through the holes in a bottle. 3. Fill the bottle with water so that the water level is above the skewer. 4. Place the bottle in a tray. Slowly & carefully remove the skewer from the water bottle. What happens? 5. Now, twist off the bottle cap. What happens?