Product Review

How many breaths does it take to fill an 8 foot long plastic tube? Just one! The Bernoulli Bag, also called the wind tube or wing bag, is a great instructional tool to teach about Bernoulli's Principle. Included in this pack, along with the four bags, is a teacher's guide. The teacher's guide not only explains how to use the Bernoulli bags, but also leads the teacher in how to instruct students about the Bernoulli bags and Bernoulli's principle. Also included in the teacher's guide are "real world applications" of Bernoulli's principle, which can be discussed with students after experimenting with the Bernoulli bags. The long plastic bag demo nicely illustrates Bernoulli's principle. Tie a knot in the end of the 2 meter x 25 cm (8 ft x 10 in) bag and stretch it out on a smooth surface. If you were to blow it up by placing it firmly to your mouth, many lung-fulls of air would be needed. But when you hold it in front of your mouth and blow, air pressure in the stream you produce is reduced, entrapping surrounding air to join in filling up the bag. So you can blow it up with a single breath! This is especially effective after your students have counted many of their own breaths in attempting to fill up the bag! -Paul G. Hewitt, Conceptual Physics Product is latex free.