Q. & A.s SCIENCE & TECHNOLOGY – 3

Q. &  A.s  ‑‑‑  SCIENCE  & TECHNOLOGY – 3

1.   Why do all metals turn red when heated?

Red is the colour that indicates the temperature of the hot metal. Red is the first colour when a metal is heated, is seen.

2.   Can animals distinguish colours?

        No.

3.   Why hair is black in colour?

        It is due to the presence of melanin present in the hair.

4.   What properties light will not have after leaving the atmosphere?

        After leaving this atmosphere light will not have interference, diffraction and polarization properties.

5.   Which light is dangerous to our skin?

        Ultraviolet.

6.   How are place values below zero measured?

Milli

Centi

Micro

Pico

Nano

Femto

Atto

7.   When drops fall on hot bulb it breaks. Why?

Glass is a bad conductor of heat. If we sprinkle water on hot glass, where water falls there it contracts and the surface facing heat expands. This unevenness in expansion and contraction is the cause of break in hot glass.

8.   Can we put our hand in  boiling water?

On Everest there is low pressure. If pressure decreases, boiling point decreases. At a height of 8.8 kms the water may boil at less than 30^o C. so we can put hand in the boiling water.

9.   Why can ‘t we cook food on Himalayas?

It is because of low pressure. As pressure is low, water boils at less than 30 degrees C. That is why we cannot cook food on Himalayas.

10.   What is temperature?

The intensity of heat that can be measured using an instrument is called temperature.

11.   Can we create a hot burning ice?

Yes. At 76 cms of mercury pressure = 1 atmosphere, water becomes ice at 0^o C. if we go on increasing the atmospheric pressure, water freezing point also rises. A point nearly 76 atmospheres pressure, the water freezes at 100^o C. if we catch that it burns.

12.     How can we increase agricultural production?

If magnetic fields are applied the agricultural production is increased.

In that experiment more seeds could be produced.

More flowers could be produced.

The harvest came earlier than the due date.

This experiment was done by Shiyajaki seed co.

The scientist was Pujiyo Shiyajaki.

13.      What is time reversal theory?

This was first proposed by Albert Einstein. If we can travel faster than earth’s rotational speed we can be earlier than the time taken by a normal flight.

If we travel in a normal plane we may reach America after two days. That means if we start on Monday we reach on Tuesday evening to America. These planes travel below 1600 kmph. If we travel in concorde we reach America on the same day. It is because concorde travel at 2500 kmph faster than earth’s rotation.

14.      A nail sinks but a ship floats. Why ?

It is the principle of Archimedes.

The weight of the water displaced by a nail is lighter than the nail itself. That is why nail sinks.

The weight of the water displaced by a ship is heavier than the ship itself. That is why ship floats.

15.    How was time calculated before AD or BC?

Kingdoms of the world had their own time calculating systems.

Hindus          Vikramaditya sakam / Salivahana Sakam

Muslims        Hijra

And so on.

To avoid that problem the British changed the system. They took birth of Christ as standard and implemented the same all over world wherever they ruled. The entire time calculation of the world is made into two sides. After the Christ and Before the Christ.

AD  Anno Domini

BC   Before Christ.

Though this system  has errors still it is accepted.

16.    A top can stand on its sharp edge while rotating. Why?

When it rotates it gains artificial gravity. That gravity makes to neutralise the natural gravity. That is why it can stand on the sharp needle while rotating.

17.      How the roads in cold countries are visible?

In cold countries during night times salt is sprinkled on the road. This salt reduces the freezing point of water. That is why the roads are clearly seen during night even in Canada.

18.      What is aurora borealis?

It is the coloured lights seen in the skies around the North Pole. The exact reason is not yet known. One reason is that over the pole the atmosphere gets ionized. This ionized gas due to some other factors such as interaction of energetic particles like electrons and protons from outside the atmosphere with atoms of the upper atmosphere, is illuminating. This happens on the upper latitudes. If the sun spot activity is more, this glow can be seen to the middle latitudes also.

19.    What is aurora australis?

It is the coloured lights seen in the skies around the South Pole. The exact reason is not yet known. One reason is that over the pole the atmosphere gets ionized. This ionized gas due to some other factors such as interaction of energetic particles like electrons and protons from outside the atmosphere with atoms of the upper atmosphere, is illuminating. This happens on the upper latitudes. If the sun spot activity is more, this glow can be seen to the middle latitudes also.

20.   A small stick catches fire faster than a large log.

For catching fire temperature is more important. A small piece of wood gets and transfers heat faster to other parts and gets ignited fast. Whereas a large log needs more heat and long time to transfer heat so that the temperature can be increased. That is why a small piece gets fire faster than a log.

21.      Why turmeric powder turns red when mixed with slaked lime?

Turmeric is slightly acidic in nature due to the presence of hydroxyl groups. Slaked lime is nothing but calcium hydroxide which is basic in nature. That is why when acid reacts with base red colour is seen.

22.      Which is easy, heating or cooling?

Heating is easier than cooling. Heating can be done with any type of fuel. But cooling requires a fridge, current , maintenance, etc.

23.      Why hot coffee is tastier than cold coffee?

Hot coffee is thinner than cold coffee. Hot coffee touches all the points on the tongue higher or lower. It travels along all the bottom and lower points. All the taste buds are touched. That is why it tasty. Where as cold coffee is thick and it touches only the top points of the taste buds.

24.      How does a submarine float and sink as desired?

The submarine contains chambers. When the chambers are filled with water it sinks. When the chambers are emptied it floats.

25.       When an electric bulb breaks it makes a big sound. Why?

The bulb contains vacuum. When it breaks the air surrounding it rushes in to fill the vacuum from all the sides. That is why a lot of noise is heard.