Forces in Fluids


Photo by Taylor Simpson on Unsplash


Fluid and motion are required for flight!

During this lesson, we explore the scientific principles that affect object in the air and in water. We explore airplanes and flight in the next lesson.

Complete the labs for the lesson. Each lab write-up is worth 20 points. Take a screenshot of the ocean pressure quiz. Turn it in or e-mail it to your teacher or parent.

This lesson will take two days to complete. Make sure that you talk with your teacher if you finish early.


Air Pressure and Air Density affect the motion of an object in fluids.

Ocean Pressure is different from air pressure. Read all about it, print, and send the quiz at the end.

Other key principles of fluid dynamics are Buoyancy, the Archimedes Principle, and hull displacement.

Download the a lab write-up for each experiment.


Review the Lesson Inquiry. When complete, turn it in or e-mail it to your teacher or parent.

Seawolf Submarine

Submarine from US Navy

Carton Experiment

  1. Collect one 950 ml and one 1.89 liter milk carton
  2. Put a hole in each of the cartons approximatly approximately 2 cm from the bottom.
  3. Work over a sink.
  4. With your finger, cover the hole in each of the cartons.
  5. Have your lab partner fill each container to about 5 cm deep.
  6. Take your finger away from the holes.

Which stream went farther? Explain your reasoning and record your results in a lab-write up.

Make the connections to preasure and fluid motion.

Air Balloon

Balloon from USGS

Ball and Straw Experiment

  1. Take a ping-pong ball and a straw.
  2. Put the straw in your mouth and tilt your head backward.
  3. Blow air into the straw and attempt to balance the ping pong ball on top of the straw with the air pressure.
  4. Record the data regarding the length of time you can support the ping pong ball on a column of air.

What happens if you try to spin the ball? Explain your reasoning and record your results.

Make the connections to pressure and fluid motion.

Done Early?

Research the history of submarines .

Hey--by the way, what is blow ballast?