Title: Bernoulli s Principle Lab Supplemented with Digital Video Designed by Burke Green and Megan Ward Purpose/Rationale: Bernoulli s Principle is useful in predicting several physical phenomena. It makes the link between fluid speed and pressure change. This is important in many industrial processes, i.e., any process that involves fluids. It can also be used as a simplified version of airplane lift. The effects are also noticeable while driving: a small car driving next to a tractor trailer will be pulled in towards the truck. These are all fascinating subjects that Bernoulli s Principle can help us better understand. The first part of the lesson will illustrate that air behaves as a fluid. The second part will illustrate some of the properties of fluids (pressure, flow, etc). Relevent SOL s PH 7 (B, E, F) Materials and Resources: Hair dryer Balloons Soda Cans String Meter stick Tape Straws Note cards Safety: If you let students use the blow dryer, make sure they keep the temperature set on cold. Make sure students don t electrocute themselves plugging it in. Students may only use straws to blow air under the note card. Students may not engage in horseplay in the lab. Procedure (55 min): For all discrepant events, refer to digital video for a demonstration of apparatus setup. For all discrepant event portions of the lesson, students will be required to complete a portion of the activity sheet. Engage (10 min): The discrepant event for this activity is the suspended balloon. Making the balloon float and then turning the blow dryer sideways shows an interesting result of Bernoulli s Principle.
Let students try this to see how far over they can get the balloon before it falls. Have them answer the first question on the activity sheet. Explore (20 min): The second part of this lesson uses the suspended cans. Assemble the apparatus as demonstrated in the video. The students are told to try to separate the cans by blowing between them. They should come together. They can try blowing different ways on the cans and drawing diagrams of proposed airflow to get the cans to separate. No matter how they blow between the cans they should find that the cans always come together. The students should also at this time answer corresponding questions on the activity sheet. Explain (10 min): There will be a brief lecture explaining what they saw, putting things together in a more organized context. Bernoulli s Principle will be used to illustrate how these things work. The students may also work on the activity sheet during this period. Elaborate (15min): The students will be given an index card and a straw. They will be asked to write, on the activity sheet, what they think will happen when air is blown, using the straw, beneath the note card when it is folded into a 3 sided free-standing structure. To help them get the right answer, first ask where the air is moving faster. Then you can ask whether the pressure is higher or lower beneath the card. The students will make their own card structures and straws. Tell them to write their predictions on the activity sheet. Will blowing beneath the structure increase or lower the pressure beneath it? Will this increase or decrease the pressure? What will happen to the card? This time will also be used to collect activity sheets. Evaluate: There are multiple aspects to the evaluation. The class will be informally assessed during the discussion portions of the lesson. Collect and assess the activity sheet for formal evaluation.
Bernoulli s Principle Activity Sheet Name Part One: Floating Balloons Balloon Balloon Continue the airflow up and around the balloons. Where the air is moving fast, the pressure will be less than the atmospheric pressure pressing in around it. 1. How is air pressure keeping the balloon upright even when the hair dryer is tilted?
Part Two: Colliding cans. 1. Can you move the cans apart by blowing between them? 2. Imagine where the air is moving fastest around the cans. Bernoulli s Principle tells us that this fast moving section will have the lowest pressure. Where is the pressure the lowest in the can system? 3. Use the picture and show air going around and between the cans to illustrate the fast moving air. Label the fast moving air and where the pressure is least. Can 1 Can 2 4. How might Bernoulli s principle affect two airplanes flying side by side? 5. If there are two connected sections of pipe with a current flowing through them (Section A has high pressure/section B has low pressure), which section (A or B) has the slowest moving current?
Part Three: Collapsing Cards 1. Here is a side view of the card. The air will flow beneath the card into the paper. Label the fast moving air and where the pressure is least. 2. Why does the card flatten onto the table instead of being pushed upward by the rush of air?