Lower Part of a Wheel Travels Slower

By Anupum Pant

Stick a colourful piece of paper on the side of a rim of a wheel and make the wheel roll away. If you observe carefully you’ll see, whenever the paper is near the ground, it appears clearly. However when the paper is at the top of the wheel, furthest from the ground, the paper appears hazy.

Also if you observe the spokes of a wheel of a moving cart, you’ll see that the spokes at the lower part of the wheel appear clearly. While the spokes of the upper part appear to blend into a single body, as if travelling much faster than the lower part.

It seems, the upper part of the wheel is travelling at a higher speed than the lower part of the wheel. How can that be, when both are physical extensions of a single object?

Yes, in fact the upper part does travel faster than the lower part. This sounds incredible, while it seems very ordinary to others who understand the simple physics of it. The physics involved really is very basic. So basic that I’m sure many reading this are cursing me for writing something so ordinary. But I find it really incredible. And believe me, there still are people who need to know this.

Let’s suppose the wheel moves at a speed of v in the right direction. However that is just the speed of the centre of the wheel. The upper part of the wheel for instance rotates at a speed of, say v, and also translates in the same direction at a speed of v. So, the speeds add up. And the top is travelling at a speed of 2v.

Similarly, at the bottom part of the wheel, the rotation is in the opposite direction (towards the left) and translation is in the right direction. Hence the speeds get cancelled and the lowest part of the wheel is stationary.

rims of a wheel

These are the topmost and bottommost points I’ve discussed here. For all the other points on the rim the rotational speed v gets split into a horizontal and a vertical component. So their speeds vary and lie in between 0 and 2v.

Some call it the cartwheel riddle.

Now, if you already knew that there’s something mind-boggling for you here. There’s another similar thing about wheels which blows my mind. Demonstrated in the video below…

Tickling Yourself

By Anupum Pant

In most cases tickling yourself is tough. That is because whenever you try to tickle yourself, at the back of your head (yes, really at the back, in a part of the brain called the cerebellum) you know that the sensation was caused as a result of your own movement. That way, the brain is able to predict the sensation and is able to nullify it.

When someone else tries it on you, the brain fails to predict the movement and the somatosensory cortex and the anterior cingulate cortex fire up to make you feel the tickle.

But have you ever tried tickling yourself with a fake hand? It still doesn’t work! Even when you don’t use your direct body part, your brain knows and can predict movement. Unless of course, the fake hand is being used by someone else. It’s interesting but believable that tickling yourself with a fake rubber hand doesn’t fool the brain. But there’s more.

In fact, if you had a tickling robot which could be controlled with a remote control, you still won’t be able to use the remote to operate it and make yourself tickle. While, if some one else had the control and they tried to control the robot to tickle you, you’d feel more ticklish. Unless, there’s a delay. It blows my mind to think about that!

What if, there was a robot which could control the remote control of a tickling robot, and you could control the first one with another remote control. Would you be able to tickle yourself using this contraption? I’m saying no, you still won’t be able to tickle yourself if there was no delay in between. What do you say?

Yes, delay is crucial here. Suppose you had a long contraption which would make movements after a few seconds of delay with respect to the control (which you have in your hand), you’d feel more ticklish, if you tried. Studies say, more the delay, the more ticklish it is.

Note: People with schizophrenia can tickle themselves, using their own hands, fake hand or something else.

Remember, I started the article with “most cases”. That is because there are a couple of ways to tickle yourself successfully. Try making little circles with a soft touch behind your knee for instance. Or use a feather on the sole of your foot. Or, try making circles with your tongue on the roof of your mouth where there’s a ribbed texture…

Weather Reporting Leeches

By Anupum Pant

Of all the creatures in the whole wide world, you’ll be surprised to know that leeches have played a fairly important role in the history of weather forecasting. An incredibly bizarre device invented by Dr. George merry weather, in the 19th century, called the tempest prognosticator, was basically a barometer powered by leeches.

Dr. George Merryweather, aptly named, was a surgeon by profession who was a lot into leeches. Since barometers were already being used for a long time then, to indicate approaching storms, he knew that air pressure was crucial in determining weather. However, Dr. Merryweather, an ingenious man, hell-bent on doing things the different way, had a different plan in his mind.

In his profession, he came across medicinal leeches all the time. In course of time, with a keen ability to notice details, he noticed that leeches were sensitive to electrical variations in the atmosphere.
He noticed a peculiar behaviour among these creatures. He observed that the leeches often started squirming around in a chaotic manner before a storm arrived.

Putting this practical knowledge to use, and experimenting with a number of designs, Dr. Merryweather devised a contraption. It consisted of 12 pint-sized bottles arranged in a circle. Each of which contained a leech in one-and-half-inch deep rain water. The top of every bottle had a tube into which the leech could crawl and disturb a mechanism, which in turn would activate a hammer to hit a bell – indicating that a storm is coming.

When a storm would come, the leeches were expected to crawl up the bottle, into the little pipe and activate a Heath-Robinson like mechanism which would make a hammer hit the bell. When the leech had completed its job it would fall down into the water and the hammer would go back to its place.

However, a number of times the leeches would give a false alarm. That was the reason he decided to use a jury of 12 leeches. And said,

The more of them that rang the bell, the more likely it was that a storm would be on its way.

If you ever go to Devon, you must take some time out to visit the Barometer World Museum to check out a full-scale working model of this device. Or you could go to the Whitby Museum in North Yorkshire to see the other working model.