How to make a balloon kebab and other delights from the Physics Buskers

Paula Croal demonstrates a clever trick with a balloon and kebab stick
20 Apr 2011 17:19:56.810

What happens if you stick a sharp stick into a balloon? It pops, right? Well, not necessarily, as The University of Nottingham’s Physics Buskers are keen to demonstrate…

The Physics Buskers — whose last appearance was at Nottingham’s Light Night — are busy brushing up their skills ready for May Fest 2011, the University’s free community open day for family, friends and alumni on Saturday 7 May.

Barbie dolls, balloons, fluorescent pens and liquid nitrogen all play a part in helping to shake off the bearded-old-man-in–white-coats image and making people realise that science is fun.

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"The aim is to raise interest in science and to let people know that it’s relevant to everyone," explains Professor Penny Gowland, of the School of Physics and Astronomy. "People from age six to 60 — they’re all interested."

"This is fun for us too," agrees lab technician Paul Munday, as he dips a balloon into liquid nitrogen. The balloon deflates completely. He removes the wrinkled balloon and blows on it gently. Within seconds it reinflates.

"The liquid nitrogen is so cold — about minus 196 degrees — that it liquefies the air inside the balloon, making it about 700 times smaller. But the air is still there, it hasn’t gone away. When it warms back up it expands again and so the balloon reinflates," he explains.

Then he pours the liquid nitrogen into a miniature steam engine; the gas that it gives off sets the engine in motion.

Other ‘tricks’ include dropping peanuts into fizzy water, writing on the audience with ‘invisible’ ink and making table-top rockets.

Paula Croal, first year PhD Physics student, demonstrates the balloon trick with a kebab stick. "This is a fab idea! I’m going to recreate this with my nephew — he’ll be amazed!"

Paula, along with Julian Sterling, has just spent several weeks working with city schoolchildren for a module on communicating science — part of the School’s outreach work.

Julian and Paula worked with year 9 students at Nottingham Academy, helping them to design and build rockets and rocket launchers.

The aim of the project was to spark an interest in the students and to make them think about studying at university. And, again, to challenge the stereotype about scientists.

"The kids were a little surprised when I turned up," says Paula. "They assumed I’d be a man!"

After two weeks working with Paula and Julian, the students created an activity for 70 year 5 pupils from Jesse Boote Primary School to do as part of a ‘trickle down’ approach.

"I was quite impressed when I heard the year 9s explaining how the physics worked to the younger kids because we hadn’t drummed it in to them, they had just taken it in during the work we were doing," says Paula.

"They really enjoyed it and by the end they all said they would definitely recommend it to another year as a worthwhile thing to do."

It’s the introduction of physics busking to The University of Nottingham that earned its creator — PhD student Claire Sweetenham — a Vice-Chancellor’s Achievement Award last year. One busking event at Nottingham’s Broadmarsh Centre attracted more than 600 people.

By now the lab has come alive with spinning lights, noises, bubbles and smoke — and lots of discussion and laughter.

Finally, one of the students practises his Barbie spiel: "Why doesn’t Barbie look like your mum?"

"Because her legs are too long."

He then plunges Barbie into a glass of water and: "Voila! Now she looks like your mum!

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More details and photos are available on request from Karen Shale on (0115) 8468545 (

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