Engineering Project Boat Building Challenge

Transcription

1 Engineering Project Boat Building Challenge In this activity, students will design and build a model boat from a set of simple building materials. To acquire these materials, you may request that students donate unwanted aluminum baking pans or pie pans. Encourage students to use available materials creatively. Students should design and construct their model boats in the classroom. Encourage them to test the boats in a water-filled sink or bucket. They cannot adequately test the propulsion and guidance systems in a sink or bucket, but they can determine whether the boat will float, how much weight it can carry, and how well the boat will withstand disturbances such as wind and waves. Have students prepare standard weights by sealing dried beans in plastic bags. Because the weights will not be standardized exactly, students should measure the weight of each bag and label it with its weight. To allow students to thoroughly test and demonstrate their boats (step 8 of the Procedure) use a large inflatable childrenʼs wading pool. Alternatively, the test may be conducted in a swimming pool, a pond, or a large tank such as a ripple tank. A very large washtub or sink could also be used. You may choose to revise the performance categories for the project to accommodate the pool or tank that you use. For example, the three categories could be replaced by a single category: to build a boat that carries the most weight from one end of the pool to the other end. Suggested Materials (per pair or group) For building the boat: 1 box of pencils (unsharpened) 1 latex balloon, large size 1 drinking straw 1 rubber band 1 disposable aluminum baking pan or pie pan 1 roll of aluminum foil 1 roll of duct tape or bottle of glue

2 2 or 3 clothespins Additional materials: meter stick or measuring tape scissors 5 or 6 waterproof weights, such as sealed plastic bags containing 10 to 20 dried beans sink or bucket, filled with water science notebook or journal for each student calculator balance or scale stopwatch pool or tank (per class) Procedure Review the introduction and the three performance categories for the project. You may also wish to add other categories, such as most elegant or most innovative design. Discuss how the same boat not be best in all three categories. The boat that travels farthest might not carry the most weight. A boat that travels in a very straight path might not travel as far as a boat that travels in a curved path. Encourage students to discuss and consider a wide variety of designs for the boat they will build. Many boat designs are possible with the use of the materials described above. Pencils may be assembled into a simple framework, and the aluminum pan can be shaped into the body of the boat. Pencils may also be used as a keel or rudder for the boat, or for other devices that help stabilize the boat in the water. The aluminum foil can be used to supplement the aluminum pan and to help hold the pencils in place. The foil can also be sculpted and taped into a shape that holds the balloon and straw assembly in place. As students construct their boats, remind them that a tear in the aluminum pan could lead to a leaky boat. Encourage students to treat the pans very carefully to avoid tears. You may wish to keep some spare pans available to replace pans that students tear or ruin. Students may also use aluminum foil to cover or repair any tears in a pan. When testing the boats in Step 8, all trials should be conducted with the same starting point and finish line. To help evaluate the straightness of a boatʼs movement, you may wish to stretch measuring tape parallel to the course. To award points in Step 9, review the studentsʼ results in each category and order the results from best to worst. Assign 10 points for the best performance, 9 points for the nextbest performance, and so on. In your critique, be sure to recognize at least one strength of each boat. If a groupʼs design for a boat did not prove successful, point out that failure can be a useful step in the design

3 process. In fact, more information is often learned from a failed design than from a successful one. Invite students to discuss what they learned from this project.

4 Answers to Analysis Questions 1. Describe the forces that affect the motion of a boat. Include a drawing to show the forces. (Answer: The forces include the thrust, which is the forward force provided by the balloon; the weight, the downward force due to gravity; buoyancy, the upward force of the water on the boat; and drag, or the resistance to the forward motion that the water provides.) 2. What problems did you encounter in designing and testing your model boat? How did you address these problems? (Answers will vary. Common problems for building a model boat include preventing leaks in the hull and repairing leaks that do occur, and designing a boat that will float and that will not tip over as it moves. Using pencils to act as a keel can help stabilize the boat, but can also slow the boatʼs speed.) 3. Analyze Review the data you recorded in the Data Table. Make a graph of weight versus speed. How did the total weight of the boat and its load affect the speed? Did the total weight also affect the distance traveled and the straightness of the path? (The graph should show that as the weight of a boat increases, its speed generally decreases. Increasing weight also decreases the travel distance, but may not affect the straightness of the path.) 4. Analyze Compare your test results to other groupsʼ results. a) Which boat was fastest? Which features do you think helped maximize its speed? How do these features affect other factors of a boatʼs performance? (The fastest boats likely had the most streamlined shape and the least weight. These features may have reduced the maximum amount of weight they could carry and made them less stable, or more likely to tip over.) b) Which boat carried the most weight without sinking? Which design features helped maximize the weight a boat could carry? How do these features affect other factors of a boatʼs performance? (The boat that could carry the most weight may have had the deepest hull, meaning its body extended the deepest into the water. This feature made the boat slower.) c) Which boat traveled in the straightest path? Which features helped stabilize the boat? How do these features affect other factors of a boatʼs performance?

5 (This boat may have had an unusually long and thin shape, or it may have had a long rudder or other stabilizing features. These features may have reduced the amount of weight that the boat could carry.) 5. Explain What are the advantages of using aluminum as the building material for a boat? (Aluminum is strong, easy to bend into different shapes, and is waterproof. It also is lighter than other metals, which helps the boat float.) 6. Evaluate Think about the experimental design of the tests you put the boat through. Were you able to control all of the variables? How easy or difficult was it to make your measurements? How should the investigation be improved to make sure the results are meaningful? (Variables that may have been difficult to control include waves in the pool or tank, the volume of air in the balloon, and the mechanism for directing air out of the balloon. It likely was easy to measure the time of the boatʼs travel and the distance across the tank or pool, but may have been more difficult to measure the actual distance of the boatʼs travel. Having more time to conduct more trials would make the results more meaningful.) 7. Apply Think about a report you would write to the managers of the ship-building company. What design changes would you recommend to make a ship faster and able to carry a heavier load? (Building a long, narrow, and streamlined boat would help it travel faster, as would increasing the power of the engines. Making the boat deeper and wider would increase the load it could carry, yet also slow its speed. Regardless of a boatʼs design, a boat generally will travel more slowly as its total weight increases.)

6 In this project, students will demonstrate the following engineering process skills: Engineering Design o Design practice Process Identify problems that can and cannot be solved through engineering Research previous solutions that have been attempted Test the solution and collect data Evaluate the design based on data collected Examine alternative solutions to a problem o Alternative engineering processes Troubleshooting Recognize that all products and systems are subject to failure; many products and systems can be fixed Repair or replace the system part(s) that are not functional Determine if changing the system or process will improve its functionality Alternative solutions Consider existing solutions and generate ideas for alternative solutions that improve benefits or reduce time, cost or risk o Role of models Using engineering models Construct models of possible solutions Give examples of how models can be used to test ideas Evaluate the design of models Applied Engineering o Engineering Classifications Transportation Identify and compare examples of transportation systems and devices that operate on each of the following: land, air, water, and space Understand that transportation has many parts that work together to help people travel Understand that transportation has many parts that work together to help people to move goods from place to place