Category Science

Electricity resulting from the application of mechanical pressure on certain crystals like quartz and tourmaline is called piezoelectricity.

When these crystals are subjected to mechanical strain, a voltage across their opposite faces.

Conversely when a voltage is applied to such crystals, they vibrate.

Piezoelectric materials are used for converting mechanical strain into an electrical signal in such devices as microphones and phonograph pick-ups. The converse effect in which a mechanical output is derived from an electrical signal output is used in such devices as headphones and quartz watches.

The phenomenon of piezoelectricity was discovered in the 1880s.

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When reading the printed matter on the wrapper of a bar of toilet soap, I saw the following: TFM = 75% written in bold letters.

What is the meaning of TFM and what is its significance?

The chief ingredients of soap are fats – manufacturers either use animals fats or a vegetable oil, like coconut oil – and an alkali, usually caustic soda. The fats are the most important part of the soap.

TFM stands for Total Fatty Matter. This expresses the real soap content in the toilet soap. If TFM is given as 75% it means that the actual soap content is 75%, while the remaining portion consists of additives, which make it foam, or give it its colour, or keep it hard.

The higher the TFM percentage, the better is the quality of the soap. It is binding on the manufacturer to state how much fatty material there is in the soap.

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A car travelling in a straight line is approaching a corner. As the driver turns the steering wheel, the car begins to swing around the corner.

We know that an object in motion tends to travel in a straight line unless acted upon by a force.

The force that makes the car turn is the friction between the car tyres and the ground. If the friction is reduced by oil or water on the ground, then it may not be great enough to provide the centripetal force and then the car will not turn but carry straight on!

If there is a passenger in the car, he too will tend to carry straight on as the car turns the corner. But friction between him and the seat provides a centripetal force to make his direction of travel circular.

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Salk’s polio vaccine has two main drawbacks; it is not completely effective against one of the three strains of polio and it gives immunity only for a limited time which means the child has to be re-vaccinated regularly.

The oral polio vaccine was developed by Albert Sabin at the University of Cincinnati. It uses a small amount of live virus unlike the Salk vaccine which uses samples of the virus which has been killed by formation.

The Sabin vaccine is given orally. It gives immunity against all three strains of polio. It does not have to be taken as often as the Salk vaccine – just three separate doses with intervals of one month each between each dose and then a booster some years later.

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A road was being laid in front of our house and a man began pulling a heavy vibrating roller over the concrete that had been spread over the road.

Why are such vibrating rollers used in road building?

Whenever you pour rice into a tall container, you shake the container vigorously from time to time so that the grains settle down making room for more.

Similarly, when concrete is laid on roads, the road has to be shaken to enable the concrete to seep down into all the nooks and crannies and fill up all the crevices, leaving no air pockets.

The vibrating roller used by road-builders makes a lot of noise but all that it is doing is shaking up the road!

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