Design a Boat

Target Subject: Technology/engineering

A boat made from aluminum foil floats in a tub of water

Author

Adapted by Yoo Jin Chung and Kate Fraser

Purpose

With properties of matter in mind, design a boat that will hold as much weight as possible.

Background Information

Density measures the amount of matter in a given volume of an object. To find the density of an object, divide the object’s mass by its volume (D = m/v). Density is a physical property, which means it is same for one substance, no matter how much of a substance is measured. Fresh water always has a density of 1g per cubic centimeter; a cup of water in your hand and water from an entire river has same density.

A buoyant object floats. Buoyancy is also a physical property. Whether an object floats or sinks in liquid depends on the object’s density. If the object’s density is less than the density of the liquid, it will float. If the object’s density is greater than the liquid’s density, it will sink. Then, how does a ship, made of dense iron, float in water? Although iron is denser than water, a ship is not a solid chunk of metal. It has a lot of rooms and empty area filled with air. Therefore, a ship has a much lower density than a solid piece of metal the size of the ship. This makes the ship’s density less than water’s density.

Preparation

Shaping the boat either in clay or aluminum foil is a tactile task. Students may need to practice a variety of shapes and methods to develop the most efficient design,

Materials

aluminum foil, clay, tub with water, metric ruler, pennies, scale

Procedure

1. You will try to design a boat that will carry the most cargo (pennies) before sinking. Your choice of material will be clay or aluminum foil. Consider which material would be the best for your boat.
2. Consider different boat designs to determine which design would be the best. Construct your model boat.
3. Measure its length, width, and height in centimeters. Approximately, what is the density of your boat?
4. Measure the mass of your cargo (pennies). Measure the mass of 10 pennies. Then, you will be able to figure out the mass of 1 penny, 5 pennies, 20 pennies, etc.
5. Test your boat design by floating it in a tub of water without pennies. According to your measurements, how many pennies do you think your boat will hold?
6. Add cargo (pennies) to your boat. Record the number of pennies you are able to add before your boat sinks.
7. Compare the result with the estimation you made in step 5. Were they close? If not, why do you think the estimation was different from the result?

If the student has not yet learned about mass and volume:

• Mass: Mass is the amount of matter in an object. Weight is different from mass. Weight may change depending on location, but mass never changes. Weight measures the pull of gravity on an object. If a person goes up to the top of the mountain, his weight will be less, because the pull of gravity on him is less. However, his mass will not change.
• Volume: Volume is the amount of space that an object takes up. Volume = Length x Width x Height.

Resources

Scott Foresman Science, Diamond Edition, Grade 5 Pearson Education, Inc. by Timothy Cooney, Jim Cummins et al., 2010, pages 344-363.