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ELI5 is an acronym for "explain like I'm 5", which people use when they want something explained more clearly. I thought that if I want to practice getting ideas across clearly, I should try explaining physics to real 5-year-olds!

I offered to do some science at my daughter's school and was given the chance to lead a session in their annual "Men Behaving Dadly" event. For this, over 100 dads spend a full Friday at school doing activities with their kids like football, arts and cooking.

For the science activity I set up two things: building Lego cars for races, and making cornstarch slime. This is a material that flows like a liquid when you leave it alone, but becomes hard like rubber when you squeeze it. A freely-availble research paper about it is described here.GWM2 ELI5

We timed each car on three runs down 4 m pieces of guttering and built up a leaderboard for the fastest cars. The kids tested the expectation that cars run faster down a steeper slope.

We made around 25 kg of cornstarch slime and quite a mess! I explained the weird behaviour of the slime using a box with a hole in the bottom to show how plastic balls can fall through the hole as long as you don't jam them up by pressing down from above.

We also set off four eruptions of Mentoes and Diet Coke (thanks Ally for the mentoes!). There's a peer-reviewed paper on the subject here (email me if you'd like a copy).

By the end of the day over 100 kids had joined in with over 30 dads.GWM3 ELI5