Build a Water Wheel
Flinn STEM Design Challenge™
Materials Included In Kit
Aluminum dishes, 40 Binder clips, 4 Caps with ½" hole, 10 Cups, 30-mL, 40 Hex nuts, 20 O-rings, 4 Paper clips, jumbo, 2
Plastic pans, 2 Pipets, super jumbo, 40 Rubber tubes, 1", 2 String Tape, masking, 3 rolls Weighing dishes, small, 40 Wood dowel rods, 12" x ¼" diameter, 2
Additional Materials Required
Balance† Glue gun and glue sticks (optional)* Marker, permanent† Meter stick† Notecard†
Scissors† Source of running water† (see Lab Hints section) Stopwatch or timer* *for each lab group †for Prelab Preparation
Prelab Preparation
Enough materials are provided to set up two testing stations.
- Fasten a binder clip to the center of each long side of the plastic pan. Flip down the outside metal arm and flip up the inside metal arm of each clip (see Figure 4).
{14057_Preparation_Figure_4_Side view}
- Insert wooden dowel rod into one of the flipped up binder clip arms.
- Insert the other end of the dowel rod into the 1-inch rubber tube. Push the tube along the rod until the tube is in the center of the rod.
- Insert the rod into the other binder clip arm. The rod should rest on the narrow portion of the binder clip arms (see Figure 5).
{14057_Preparation_Figure_5}
- Cut a 65-cm length of string.
- Tie a large knot at one end of the string and thread the knot through one of the O-rings.
- Making sure the knot remains threaded through the O-ring, place the ring onto the dowel rod, 1.5 cm from the end.
- Place a second O-ring at the very end of the dowel rod (see Figure 6).
{14057_Preparation_Figure_6}
- Tie the free end of the string to a paper clip.
- From the top of the paper clip, measure 50 cm along the string and mark this length on the string with a permanent marker.
- Pull the knotted end of the string that is through the O-ring until the 50-cm mark is at the bottom of the dowel rod, so from the dowel rod to the paper clip measures 50 cm (see Figure 7).
{14057_Preparation_Figure_7}
- Set the pan with the dowel rod along the edge of a lab counter or table so the paper clip hangs down freely and the string does not rub against anything when the load is lifted during testing.
- Repeat steps 1–12 for a second testing station.
- Weigh ten hex nuts on a balance to determine the average weight of each nut. Write the average weight in N on a notecard and post by each testing station. Note: 1 g = 0.0098 N. For a simplification, multiply the amount in grams by 0.01 for an approximate conversion to newtons.
- Attach 5 hex nuts to the paper clip hanging from each dowel rod. Pinch the paper clip closed to secure the hex nuts.
- The string should wind up between the two O-rings during testing.
- For testing the final water wheel designs in Part B, add five more hex nuts to each paper clip for a total of 10.
Safety Precautions
Remind students to use caution when cutting with scissors. Wear safety glasses during testing. If testing indoors, wipe up all water spills immediately. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory.
Lab Hints
- Enough materials are provided in this kit for 30 students working in groups of three or for 10 groups of students. Both parts of this laboratory activity can reasonably be completed in two 50-minute class periods. The pre-laboratory assignment may be completed before coming to lab, and the data compilation and calculations may be completed the day after the lab.
- To optimize a fair test, the running water must have a consistent flow rate. A few suggestions are given.
- If a lab sink has a serrated nozzle, attach plastic tubing to the nozzle. Hold the end of the tubing a set distance over the water wheel and find a good setting on the faucet for a steady flow of water that is not too forceful. Mark this setting with tape.
- Set up a support stand with a ring clamp and place a funnel in the ring. Fill a large pitcher or water jug (2-4 L). Stopper the funnel stem and fill the funnel with water. At the same time the stopper is removed, pour water steadily into the top of the funnel so the water level in the funnel remains constant.
- Challenge your students to come up with a way to ensure a consistent flow of water. Let their creativity flow!
- For indoor testing, place a large towel or tray such under the plastic pan to contain splashes of water. A large demonstration tray is available from Flinn Scientific, Catalog No. AP5429. If any water splashes onto the floor, wipe up immediately.
- Start each test with five hex nuts for the load. Adjust the load if none of the prototypes can lift it or if all raise the load very fast. For the final test, use 10 hex nuts at each station. Additional weights or standard hanging weights may be used to determine the maximum load a water wheel can lift.
- The water wheel prototype is constructed without glue to allow ease of modifications. Once students have chosen their final design, you may decide to allow the use of glue. Hot glue or other water-proof adhesive for binding plastic to plastic should be used. Consider the experience and maturity of your students and set specific design constraints accordingly.
Teacher Tips
- This activity may be used in conjunction with a unit on engineering design, transfer of energy or renewable resources. Students should have prior knowledge of types of energy such as mechanical, kinetic and gravitational potential.
- More advanced students can research the Pelton wheel, designed to make maximum use of the impulse (change in momentum) of the moving water. Challenge students to design a Pelton wheel and compare its power output to the original prototype.
- Students may further research hydropower as it is used today, particularly hydroelectric power.
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering Practices
Asking questions and defining problems Developing and using models Planning and carrying out investigations Analyzing and interpreting data Constructing explanations and designing solutions Engaging in argument from evidence Obtaining, evaluation, and communicating information
Disciplinary Core Ideas
MS-ETS1.A: Defining and Delimiting Engineering Problems MS-ETS1.B: Developing Possible Solutions MS-ETS1.C: Optimizing the Design Solution HS-PS3.B: Conservation of Energy and Energy Transfer
Crosscutting Concepts
Cause and effect Scale, proportion, and quantity Systems and system models Patterns Structure and function
Performance Expectations
MS-ETS1-2. Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem. MS-ETS1-4. Develop a model to generate data for iterative testing and modification of a proposed object, tool, or process such that an optimal design can be achieved. HS-PS3-2. Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motion of particles (objects) and energy associated with the relative position of particles (objects). HS-PS3-3. Design, build, and refine a device that works within given constraints to convert one form of energy into another form of energy.
Answers to Prelab Questions
- Why is water considered a renewable source of energy?
The amount of water on the Earth and its atmosphere is constant. Using water to power a water wheel does not reduce the amount of water available.
- A student lifted a backpack weighing 80 N to a desktop that was 0.76 m high. How much work did the student do?
Work = 80 N x 0.76 m = 60.8 J
- Two students volunteered in the library. They were assigned the task of lifting books from a cart to a shelf. Each book weighed 10 N. Kayla’s shelf was 1 meter above the cart and she shelved 20 books in one minute. Noah’s shelf was 0.5 m above the cart and he shelved 48 books in 90 seconds. Who generated more power in shelving the books? Show your work.
Kayla: Force = 10 N x 20 = 200 N
Work = 200 N x 1 m = 200 J Power = 200 J/60 s = 3.33 W
Noah: Force = 10 N x 48 = 480 N
Work = 480 N x 0.5 m = 240 J Power = 240 J/90 s = 2.67 W
Kayla produced more power than Noah.
Sample Data
Part A. Build a Model Water Wheel
Write a description or draw and label the chosen water wheel design.
Removed stems from pipets and cut across each bulb to make a 2-cm diameter bucket that was 2.5 cm deep. Arranged seven buckets around wheel, fairly evenly spaced. The sides of the bulbs were pressed onto the tape around the wheel.
Data Table A. Weight of load: ___0.14___N Distance lifted: ___0.5___m
{14057_Data_Table_1}
Part B. Design Challenge Write a description or draw and label the chosen water wheel design. The pipet-bulb buckets were cut in half lengthwise to form a scoop. Pressed the rounded end of each bucket onto the tape around the wheel so the open end of the scoop faced away from the wheel. Used 8 buckets very evenly spaced around wheel. Data Table B. Weight of load: ___ 0.28___ N Distance lifted: ___ 0.5___ m
{14057_Data_Table_2}
Answers to Questions
- Calculate the work done by the modified water wheel from Part B and record in Data Table B.
Work = F x D W = 0.28 N x 0.5 m = 0.14 J
- Calculate the power generated by the modified water wheel for each trial and the average power output. Fill in the data table.
Power = Work/Time P = 0.14 J/8.45 s = 0.018 W
- How did the amount of power generated by the original water wheel design compare to the modified design?
The modified design generated over 3.5 times as much power as the original design. It not only lifted more weight, it did so in less time.
- Describe how energy is transferred throughout the water wheel system, starting with energy from the Sun and ending with the lifted load.
Energy from the Sun drives the water cycle of evaporation, condensation and precipitation. Gravity causes water on the Earth to flow. The kinetic energy of the moving water fills a bucket on the wheel, and the turning wheel gains kinetic energy. As the wheel turns, the next bucket fills with water, and so on. When the filled buckets reach the bottom of the turning wheel, the water empties and the buckets continue up the other side, to be filled again. The mechanical energy of the turning wheel is transferred to the dowel rod, causing it to spin. The spinning rod winds up the string and lifts the load. The load has kinetic energy as it is being lifted, and ends with gravitational potential energy when it stops at the rod.
- The largest water wheel in the world, called the Laxey Wheel, measures 22.1 m in diameter and is 1.8 m wide. It was used to pump water out of underground mines on the Isle of Man. The water wheel could move a volume of water weighing 10,780 N a distance of 640 meters in one minute.
- How much work in joules was the wheel capable of producing?
Work = 10,780 N x 640 m = 6,899,200 J
- How much power could the Laxey Wheel produce? (Reminder: Power is the rate of work done per second).
Power = 6,899,200 J/60 s = 114,987 W
References
Hydropower. Secondary Energy Infobook. National Energy Education Development Project. http://www.need.org/files/curriculum/guides/Secondary%20Energy%20Infobook.pdf (accessed January 2016).
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