Build a Life Jacket
Living on a deserted island may require some trips into the ocean to collect sea life. Floating on the ocean is part of survival! What object helped Michael float when he went overboard? In this exploration students use a limited set of materials to design and build a flotation device that can keep an unopened can of soup/vegetables afloat in a bucket of water for 1 minute.
Materials Required
• Basin or bucket
• Can of soup or vegetables
• Towels
• Water
Engineering Materials (all of the items are not required, find items around the house)
• Drinking straws
• Balloons
• Plastic sandwich bags, non-zip
• Foam packing pieces (many pieces of various shapes/sizes)
• Packing pillows
• Corks
• Rubber bands
•.Duct tape
Procedure
A personal flotation device (PFD), or life vest/jacket, is designed to keep a person afloat with their chin above water in the event of an emergency. The most ancient examples of primitive life jackets can be traced back to inflated animal bladders.
1. Draw a face on the can and design a Personal Flotation Device (PFD) that keeps the face above water at all times.
2. The goal is to keep the can afloat for 1 minute.
3. Design, build and test your prototype.
4. Test and redesign as necessary.
5. Take a picture of your final prototype before the final test.
6. Final Test - You will have 30 seconds to get the PFD on the can and the can into the water!
7. Some tips:
• Use balloons, foam pieces, or corks to design a PFD that keeps the can afloat.
• You may decide to build an inflatable device or a passive flotation device.
• Straws may be used to inflate balloons or sandwich bags after the flotation device is placed on the can.
Questions
1. Why do you think a soup can sinks?
2. What are some things that float?
3. What do you wear to help you float when you go swimming? Or what have you seen people wear/use to help them float?
4. What do you think people used before modern PFDs were invented? (Life jackets made of cork were available in the early 19th century. Inflatable life vests were invented in 1928.)
5. What worked and what didn’t work?
6. What would you do differently?
7. Think about modifying your prototype or try a completely new design.
8. Evaluate the success of each design:
9. Did the can stay afloat for at least 60 seconds?
10. Did the can float horizontally? Vertically?
11. What if the can were a person—how would it float?
Discussion
Objects that sink have more force in the downward direction than objects that float.
A fluid exerts an upward force on objects less dense than itself. An object floats if water’s density is greater than the object. A life jacket is filled with a very light material, usually foam, that can displace a lot of water compared to its weight. The principle of buoyancy holds that the buoyant or lifting force of an object submerged in a fluid is equal to the weight of the fluid it has displaced. The concept is also known as Archimedes's principle, after the Greek mathematician, physicist, and inventor Archimedes (c. 287-212 B.C. ), who discovered it.
Fluid Displacement - Occurs when an object is placed in a fluid, pushing the fluid out of the way and taking its place.
Opportunities to read more: Reread the part of the book in which Michael uses his football for flotation and then read more about Flotation devices throughout history