Water, gravity and Isaac Newton

Water, gravity and Isaac Newton

Set up time

You’ll need 15 minutes to set up.

What you need

Disposable plates, plastic cups, wooden skewers, stapler, 1L milk cartons, string, masking tape, jug/tap, bucket, water


Through a range of experiments, demonstrate how water and gravity can be converted into movement (kinetic) energy, and then harnessed as electricity.

Learning outcomes


Your students will learn about Isaac Newton’s Third Law, that for every action there is an equal and opposite reaction.


Your students will observe and record results from a scientific experiment, using scientific terms.


Your students will learn how to extrapolate from these simple experiments to consider the principles and benefits of hydro energy.

Instructions: Water wheel

On two plates, mark the centre point and six equal segments around the edge.

Staple the plastic cups to each segment, and then join the plates through the centre using a skewer.

Holding the skewer, pour water into a cup at the top of the water wheel and observe the effects.

Discuss what happens when water is poured in slowly, then fast. Ask students to identify the energy transfers at work.

What makes the water fall out of the jug and into the water wheel?
How can the movement (kinetic) energy of the water wheel be used to supply electricity?

Instructions: Milk carton effect


Punch a hole in the top of the milk carton, and thread a long piece of string through it.


Punch a small hole in the bottom right-hand corner of each side of the carton, and cover these holes with masking tape.


Hang the carton somewhere it can swing freely (remember, you should be able to collect the water or let it fall on a garden).


Before you fill the carton with water and remove pieces of tape one by one, ask students to predict the results.

How does this experiment demonstrate Newton’s Third Law of energy?
What modifications could you make to explore the principles of energy transfer?

Extension: If gravity was removed?

What happens when you try to pour liquid if gravity is removed? This video shows NASA astronauts popping water balloons in space – where there is zero gravity – with eye-popping results.

The acceleration of objects as they fall to the ground, thanks to gravity.


Up in space, liquid doesn’t fall to the ground. The force or pull of gravity is the missing element. 


The experiments above clearly wouldn’t work in space. What types of renewable energy could be harnessed in space?


Discuss the importance of Newton’s Third Law in many of the ways that we convert energy into usable forms.