Investigations with hot air and floating balls

Today we were talking about air.
We know that air from a hairdryer is usually warm.
We wondered if the air comes out of the hairdryer and goes straight up, or whether the air goes sideways too.
We tested this by putting our hands on top of the air stream (we could feel the warm air) and then to the sides of the air stream (where we couldn't feel any warm air).
Based on this we decided that warm air travels straight out of the hairdryer.

Teacher had some balls.

The polystyrene ball is filled with polystyrene and is very light.

The ping pong ball is hollow (but filled with air) and is very light.

The bouncy ball is filled with rubber and is heavier.

The marble is glass throughout and is heavy.

We wondered would any or all of these float on the air from the hairdryer?

We ordered them in various combinations of which we thought would float best?

We also discussed how they might float.....straight up and stay there....straight up and then bounce up and down in the air......straight up but then be knocked out of the air stream.....not float at all.

We discussed what difference we thought size and weight would have on each ball.

Then the fun part.....

The testing:

Then, using a toilet roll and then a kitchen roll insert (along with 2 ping pong balls and a bouncy ball), we tested how many balls would float if we put them in in different orders.

This was really fun.

Go on, ask us what we discovered and why?