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Windbag challenge, spray straws and definitions . Miss Laverty 2012 ***experiments, lesson and worksheet adapted from the Edmonton Public curriculum book ***. March 8 th , 2012. Hand out the work books Grab today’s handout Sit down and show me you are ready to try the “windbag challenge” .
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Windbag challenge, spray straws and definitions Miss Laverty 2012 ***experiments, lesson and worksheet adapted from the Edmonton Public curriculum book ***
March 8th, 2012 • Hand out the work books • Grab today’s handout • Sit down and show me you are ready to try the “windbag challenge”
Windbag Challenge • Challenge: to inflate this bag as much as you can with just one breathe • Materials: long plastic bag (or an actual windbag if you have one) and a person with strong lungs
Windbag Challenge • Describe the method that got the bag to inflate the most in just one breath? • The bag inflated more when we made a larger opening and held it near our mouths without making a seal
Windbag Challenge • Draw a diagram to represent how we inflate the bag so easily. Be sure to show the direction of the air flow and “high pressure” and “low pressure” (HP and LP) in your diagram. Use colours to represent the low and high pressures
Windbag Challenge • How is this example of Bernoulli’s principle? • BP states that fast moving air exerts less pressure on the surfaces that it passes over • Since the air is moving quickly, we know that it is creating a low pressure area as it enters the bag
Spray Straws • Materials: drinking straws, plastic cups, and water • Procedure: • Fill a glass about three quarters full of water • Secure one straw inside the plastic cup with one end in the water • Take a second straw and hold it perpendicular to the first straw • Blow through the horizontal straw
Spray Straws • How does the fast moving air lift the water? • the fast moving air creates a low pressure area at the top of the vertical straw • The normal air pressure of the room is now considered high • We know that air moves from high to low pressure • So since there is a low pressure area at the top of the straws, the normal air pressure of the room is able to lift the water up the vertical straw • The water sprays when it goes up the straw because it gets into the fast moving air stream
Spray Straws • Real life example: • Paint sprayer/airbrush
DEFINE • Bernoulli’s Principle: • When air moves quickly it exerts less pressure over the surfaces that it passes over • Examples: funnel and ball, pop cans, paper tents, toilet paper, strip of paper, spray straws • http://www.youtube.com/watch?v=bv3m57u6ViE
DEFINE • Lift: • upward force which acts against the force of gravity
DEFINE • Gravity: • A force that attracts all objects with mass to the Earth
Gravity Bill Nye: http://www.youtube.com/watch?v=hZi8TXtRRYg