## LESSONS: Fluids

###### The majority of lesson ideas below require minimal resources other than the smartphone, and are relevant to introductory physics in high school and college. However, creative individuals are using smartphone science in more complex ways, with drones, engineering kits, and much more. Follow us on Twitter @PhysicsToolbox and see our Publications page for additional content. ###### Measuring Height and Vertical Speed with Air Pressure

What is the relationship between the PRESSURE and HEIGHT above ground?

Try This

Using the Barometer tool, determine the relationship between air pressure and height above ground. A meter stick can be employed to determine the height above ground (by measuring and counting the heights of stair steps, for example).

Related Resources ###### Liquid Pressure and Stevin's Law

What is the relationship between PRESSURE and DEPTH below the surface of a liquid?

Try This

Using the Barometer tool, place the smartphone inside of a water-proof case and submerge it under a still container of water. Use a meter stick to measure the depth of the device below the surface. Determine the relationship between pressure and depth for water. Perform the same experiment with different fluids (soap, saturated salt water, oil, alcohol, etc.)

Challenge Yourself

• Create a graph of Pressure vs. Depth for water, and derive a mathematical expression for this relationship.

• Create additional graphs of Pressure vs. Depth for other fluids, and derive mathematical expressions for these relationships.

• If there are any constants in these mathematical expressions, explain their significance.

• Using prior understandings about fluid pressure, determine the density of each fluid studied.

Related Resources ###### Air Pressure in a Balloon

What is the relationship between PRESSURE and RADIUS of an inflated rubber balloon?

Try This

Using the Barometer tool, place the smartphone inside of a spherical translucent latex balloon. (Alternatively, us an app such as Airmore to display Physics Toolbox on your computer via a bluetooth connection). Inflate the balloon, and periodically measure the radius of the spherical balloon using a meter stick.

Challenge Yourself

• Create a graph of Pressure versus Radius. and derive a mathematical expression to model the relationship.

• If there are any constants in these mathematical expressions, explain their significance.

Related Resources ###### Investigating Elements of Bernoulli's Principle

What is the relationship between PRESSURE and DEPTH below the surface of a liquid?

Try This

Using the Barometer tool, place the smartphone inside of a "wind tunnel" constructed from PVC tubes and a hair dryer. Observe changes in pressure as a result of changes in tunnel radius.

Related Resources ###### Gas Pressure and Speed in an Elevator

What is the speed of an elevator shaft?

Try This

Using the Barometer tool, measure changes in atmospheric pressure up and down a long elevator ride. Using Stevin's Law, which relates fluid pressure and depth (or altitude), determine the displacement of the elevator in the given time, and calculate average velocity during the constant velocity portion of the ride.

Challenge Yourself

• Create a graph of Pressure vs. Time for a ride up and down the elevator.

• Perform column calculations to create a graph of Position vs. Time

• From the Position vs. Time graph, determine the average velocity of the elevator during each major segment of motion (going up at a constant speed, going down at a constant speed, stopped).

• Collect accelerometer and barometer data at the same time (in Multi Record mode), and compare the graphs of Position vs. Time, Velocity vs. Time from the barometric data and the Acceleration vs. Time from the accelerometer data.

Related Resources