Unit 3: Weather

1. Unit 3: Weather Mr. Chapman Science 10

2. Air pressure • It may be surprising, but air is a fluid. • Definition of Fluid: • a substance, as a liquid or gas, that is capable of flowing and that changes its shape at a steady rate when acted upon by a force tending to change its shape. • As you may already know, fluids exert PRESSURE on their surroundings. The air we breathe is no different; it exerts pressure on everything around us. • AIR PRESSURE IS APPROXIMATELY 15 LBS/INCH2

3. Air Pressure & Air Speed • Air speed: The speed at which air is travelling • Their is a direct relationship between air speed and air pressure, and the goal of today’s activity is to determine how air pressure and air speed are related. • Once you know the answer to this question, you should be able to explain why the roofs get blown off of these houses: • http://www.youtube.com/watch?v=lJbz0EuUSlA • http://www.youtube.com/watch?v=7K-ctyHRC1s

4. Activity #1: Cans on Straws Set up two cans on straws as seen in the picture above. Blow air between the two cans. What do you observe?

5. Activity #2: Beaker Straw Fill a 400 mL beaker with approximately 300 mL of water Place a straw in the center of the beaker with water; hold the straw up in place With another straw, blow air across the top of the straw that you are holding in place. What do you observe?

6. Activity #3 Magic Coaster? ** Perform this activity over a sink Note: This activity has nothing to do with air speed, but has EVERYTHING to do with air pressure. Fill a water cup approximately half-full with water Place a coaster over the top of the cup and hold it tightly over the sink as you FLIP THE CUP OVER. Release the coaster (OMG) WHAT DO YOU OBSERVE?

7. In-Class Conclusion • State the purpose / goal of the 3 activities that you performed in class on Friday. • Describe what you observed at each station. • Explain in general terms what was occurring with relation to air speed and air pressure at each station based on your observations. • Note: although activity 3 had nothing to do with air speed, explain what was occurring anyway. • What general principle can you deduce based on your observations and explanations for each activity? • Explain why high wind speeds cause the roof of a house to come off based on the conclusion from the 3 activities.