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Spinning Eggs

Public summary: 

Can you tell the difference between a hard-boiled egg and a raw egg without breaking them?

How to test if an egg is uncooked or hard boiled.
Useful information
Kit List: 

Eggs, a mixture of uncooked and hard boiled (you'll probably want more hard boiled ones, as they tend to crack).

Packing Away: 

Dispose of eggs sensibly.

Frequency of use: 

Basic experiment
Spin an egg, either cooked or fresh.
Stop the spin with one finger for a moment, then let go.
The fresh egg will start spinning again because the inside of the egg will carry on spinning when the outside stops and will cause the outside to accelerate again. The cooked egg will stop dead.
It's probably nicer to get people to try to think of ways to tell the cooked and uncooked eggs apart before you show them how to do it! After you have explained why the uncooked eggs carry on spinning get the kids to spin a random egg and tell you whether they think it's cooked or uncooked.

Other stuff to talk about
You can also ask them what would happen if you filled an egg with syrup and spun it and stopped it? Would it spin for a longer time or a shorter time than an uncooked egg? It should spin for much less time than an uncooked egg as it is very viscous and therefore the momentum diffuses much faster through it (don't use words viscous, momentum or diffuses though).

You could also try explaining why it's harder to spin an uncooked egg then a cooked egg. I found it a bit complicated to explain but if you talk about the fact that when you spin the egg initially only the egg shell and the fluid very close within the egg (in the boundary layer of the fluid) actually spins and then more and more of the fluid starts to spin but this slows down the fluid that was originally spinning (this is due to momentum diffusion with the fluid).

If you're feeling brave...
Apparently if you spin a hard boiled egg fast enough on a very smooth surface it will start tipping upwards and spinning around its axis of symmetry rather than lying flat (not unlike those toys you can't knock over I suppose). That is, at fast enough speed the stable orbit becomes the upright one rather than the flat one. Not sure how easy this is to make work in practice though...

Risk Assessment
Date risk assesment last checked: 
Thu, 23/01/2020
Risk assesment checked by: 
Conor Cafolla
Date risk assesment double checked: 
Sat, 25/01/2020
Risk assesment double-checked by: 
Beatrix Huissoon
Risk Assessment: 

Spinning and stopping fresh and cooked eggs

Hazard Risk Affected Person(s) Likelihood Severity Overall Mitigation Likelihood Severity Overall
Smashed eggs If dropped on the floor eggs may smash, causing a slip hazard. All 3 2 6 Spin eggs in a shallow tray to reduce risk of dropping them and/or perform experiment well away from table edges.
Have equipment available to clear up broken eggs (e.g. paper towels).
If breakage does occur, watch the area until it's clean and don't let kids run around (they shouldn't be running around anyway).
Call a first aider in the case of an injury.
1 2 2
Eggs Some people have very severe egg allergies (especially raw egg). Visitors 2 3 6 Ask if comfortable with eggs around, and the possibility things might get a little messy.
If an egg is broken ensure it is thoroughly cleared up, keep visitors away from area until area has been cleaned.
Anyone with a level of allergy which might cause a major issue should be carrying appropriate drugs etc and they (or their carer) will know what to do. Risk is no greater in this case than going into a supermarket.
Call a first aider in the event of an emergency.
1 2 2
Contaminated eggs (salmonella) Salmonella risk from raw eggs. All 2 3 6 Lion-marked eggs have been declared salmonella free so should not be a problem.
We won't know that someone has salmonella poisoning until well after an event.
We might wish to warn people of the salmonella risk in the event of contact with a raw, non-Lion-marked egg, but really the risks are substantially lower than those incurred in baking a cake.
Don’t allow people to ingest raw egg / lick fingers having touched a broken egg etc.
As above, ensure egg breakages are cleaned up as soon as possible.
1 3 3
Publicity photo: 
Experiment photos: