STEM water wheel

by Fellowship Agency June 8, 2018

Looking for a STEM project that gives you the perfect opportunity to get outside with your class? This #WhatsInMyTray activity shows you how to use recycled materials to make a water wheel and explores the forces involved in making it work.

Learning Outcomes

You will be able to:

  • Construct and power a water wheel.
  • Describe the forces involved in the operation of a water wheel.
  • Measure the rate of revolution of a water wheel and calculate revolutions per minute.

You will need:

  • 1 x Extra Deep Gratnells (F25) tray
  • 2 x Plastic plates
  • 1 x Wooden dowel approximately 35cm long
  • 7 x Identical recycled plastic pots (yoghurt pots, plastic or cardboard drinking cups, film canisters, etc.)
  • 1 x Waterproof tape
  • 1 x Watering can full of water
  • 1 x Scissors
  • 1 x Ball of blue tack (optional)
  • 1 x Stopwatch
  • 1 x Permanent marker pen

What to do:

Take a look at our STEM Water Wheel What’s In My Tray activity video on YouTube here.

  • Using the point of the scissors, make a hole in the centre of the two plates big enough for your wooden dowel to fit comfortably through.
  • Slide the dowel through both holes leaving enough space between the plates for the plastic pots. The plates should be back to back.
  • Tape the plastic pots between the two plates, resting on the outer rim of the plates. Ensure all the pots are an equal distance apart and facing in the same direction.
  • Rest the wooden stick on either side of the extra deep tray and fix in place with some tape or blue tack. You can also place some blue tack around the dowel if the water wheel is sliding along the length of the dowel and catching on the inside of the tray.
  • Use the watering can to slowly pour the water into one of the cups. Do not move the watering can. As the first cup fills and falls, the wheel will spin, the next cup will move under the water stream, fill and fall, which will accelerate the spinning.
  • Take a photograph of your completed water wheel.
  • Mark one of the pots with a permanent marker pen to identify it from the rest. Use a stopwatch to measure the time it takes for the wheel to make one complete revolution. Calculate the rate of revolutions per minute (rpm).
  • Make a video of your water wheel in action. You can time the revolutions in real time or time them from the video.

What is happening:

Key words: Gravity, Kinetic Energy, Mechanical Energy, Electrical Energy, Hydropower, Hydroelectric Power.

Hydro means water, hydropower is something that gets its power from water. Water wheels, or turbines, use hydropower. Water wheels convert energy from the movement of water, known as kinetic energy, into mechanical energy. If a generator was connected to the water wheel, the mechanical energy generated could be turned in to electrical energy, which is more commonly known as electricity, or hydroelectric power.

Hydroelectric dams operate using these principles and generate large quantities of green energy. i.e. energy generated without the burning of fossil fuels.

Water gains kinetic energy when it falls. In hydroelectric dams this fall can be from a great height. The water falls due to the force of gravity acting upon it. In our model, the water is falling from the watering can.

The higher the water is poured from, the more kinetic energy it will gain, the more mechanical energy will be created and the faster the water wheel will spin.

Other things to try…

  • Try holding the watering can at different heights, e.g. increase height by 20 cm at a time. What effect does an increase in the height of the watering can have on the speed of the water wheel? Record your results in a table and then plot them on a graph of speed v’s height (y = speed (rpm), x = height (cm)).
  • Try using different types of recycled plastic pots e.g. film canisters, mini yoghurt pots, try out different sizes and see what effect it has on the revolution speed of the water wheel. Record your results in a table.
  • What other variables could you investigate? Design an investigation to test another variable, e.g. size of plate, size of water stream (bigger or smaller spout size), number of pots.
  • Is all the kinetic energy converted into mechanical energy? i.e. is your water wheel 100% efficient?
  • Can you attach a simple generator/electric motor to your water wheel? What design modifications would you undertake to achieve this?
  • Research water wheels, can you find real life examples? What are they used for? What have they been used for in the past? Is there a water wheel or water turbine nearby that you could visit? Share your research with a classmate, make a poster/display to accompany your model or put together a presentation. This section could be covered before the practical activity to provide appropriate context.
  • Display your model and water wheel research at a STEM fair or open evening.
  • Share your water wheel photographs and videos on social media using #WhatsInMyTray and tag @Gratnells

Health & Safety

As with all Gratnells Learning Rooms What’s In My Tray activities, you should carry out your own risk assessment prior to undertaking any of the activities or demonstrations.