What you need:
A large plastic bottle
An outdoor space
Cut a hole about 1cm across in the side of the bottle and stand it on the ground.
Keep your finger over the hole and fill the bottle with water.
Take your finger away – water should spurt from the hole.
Repeat what you did, but drop the bottle from above shoulder height as you remove your finger. This time, no water pours from the bottle while it falls.
Results & explanation
In the standing bottle, gravity pulls on the water so it presses on the bottom and sides and escapes through the hole. When you drop the bottle, both it and the water fall at the same rate so the water doesn’t press on anything – it’s as if it was floating inside the bottle.
PS – Marvin & Milo are © IOP and can be freely used in schools. Please do get in touch if you’d like to modify or use them for commercial purposes.