We know cats are capable of landing on their feet.

But a teacher in Taiwan is learning the hard way that holding a cat over your head and then suddenly dropping it onto a hard floor, in front of dozens of students, may not be such a smart thing to do.

The teacher – identified in Taiwan news reports as Mr Lee Feng – was trying to demonstrate a principle in physics known as the “conservation of angular momentum”.

That principle says it is impossible for an object that is not spinning to suddenly rotate without external influence.

In other words, cats shouldn’t be landing on their feet if they aren’t pushing off anything, say a wall or the hands of the person dropping them.

Yet, they do.

Scientists explain that a cat has a natural balancing system called the “righting reflex” that allows it to quickly reorient itself and land on its feet.

It also has an extremely flexible spine that lets its upper and lower body rotate in opposite directions, allowing it to use the inertia of its own body to spin rapidly.

Mr Lee was apparently inspired by videos on YouTube that show cats being dropped from a height to show how they can land on their feet using the very same principles of physics that they seem to defy.

But in most of these videos, the cats were falling onto something soft, like a bean bag or a sofa cushion.

‘Bad demonstration’

Mr Lee dropped his own cat – named Laifu – onto a hard floor, not once, but twice, and that made all the difference.

The cat could be heard hissing as it fell.

“It is fine to do this with a cat, but we cannot do it with a dog,” Mr Lee says in a video taken and posted online on March 5 by one of his students.

But he was pilloried online for what many said was his callous disregard for his own cat’s safety.

“Shouldn’t being a teacher teach children to love and respect life? This was such a bad demonstration,” Ms Page Hsu said on Mr Lee’s Facebook page.

Ms EKimi Chan, commenting on the same page, said Mr Lee should have performed his little experiment “in a safe environment”.

Others were more catty.

“So, people like this can be teachers?” said Ms Nancy Hsu.

Ms Joan Maltby-Hicks said Mr Lee should be charged with animal abuse, while Mr Zeng Li Ren remarked: “I can imagine him demonstrating jumping off a building to prove some science principles.”

There were those who sided with Mr Lee.

A Facebook commenter, Mr Jasper Wong, said: “The distance is so low, right? What’s the fuss?”

He’s sorry

Mr Lee has since apologised.

“As the owner of Laifu, I ignored the physical and mental harm to it brought by the experiment. As a teacher, I behaved controversially without considering that it would have a potential negative impact on my students and others,” he said in a Facebook post.

He said he took Laifu for a veterinary check-up after the experiment. He also donated NT$50,000 (S$2,112) to the Taiwan Homeless Animal Rescue Association.

He said he adopted Laifu from a charity, and that it sleeps on his bed every night.

He also apologised to his cat.

“I will buy you the best feline food to show how sorry I am,” he said.

The website of pet food maker Purina says that while cats may always land on their feet, they don’t always survive a fall.

A 1987 study in New York showed that nine out of 10 cats will survive a fall from multi-storey buildings.

But those that fall from greater heights – say, between seven and 32 storeys – come out with far less injuries than those who fall from less than six storeys high.

Scientists think that the higher the fall, the more time cats have to be able to right themselves and slow down their descent.