Q. & A.s SCIENCE & TECH. – 4

Q. &  A.s  ‑‑‑  SCIENCE  & TECH. – 4

1.   The track or road are banked at bends.. Why ?

At bending points, the outer side of the track is higher than the lower side. Necessary centripetal force is created to maintain the train on the track. Otherwise in the tangential direction the train jumps from the track.

2.   We cannot put off petrol fire by water. Why?

Petrol is thinner or less dense than water. So it floats on water. If we use water to put it off it comes on to the surface of the water and burns. That is why foam type extinguishers are used.

3.   Why there is gap between two rails when joined together in a railway track?

Iron expands due to summer heat or frictional heat. It contracts during winter season or normal time. If this expansion and contraction goes on for years, at the point of joining the two rails gets joined. Then that one is removed and new ones are placed keeping space between them. If the space is not left at the joint it bulges. The train derails.

4.   Breathing on mountains is difficult. Why?

On top of mountains the density of air is less. Oxygen percentage is also less. That is why breathing becomes difficult.

5.   Why can’t we write using ink or ball pen in space?

It is because there is no air pressure.

6.   When we climb mountains we bend forward. Why?

It is to maintain equilibrium. The line of centre of gravity falls in the base.

7.   When a running bus stops we fall forward. Why?

The entire body is in inertia with the moving bus. When it stops our legs part comes to halt but the body is still in motion. That is why we fall forward.

8.   When we put ice in a tumbler, moisture is seen on the outside of the tumbler. Why?

The ice in the tumbler cools the surroundings of the tumbler. The moisture in that little quantity of air accumulates on the tumbler.

9.   When thermometer is placed in boiling water the temperature does not rise after 100^oC. Why?

We can see rise in temperature upto 100oC only. After that whatever heat that supply is utilised to change the state of water from liquid to vapour.

10.    What is regalation?

When force is applied on ice, at the point of applied force it melts. When the force is removed it gains its original shape. This is called regalation.

11.    How do people skate on ice?

The weight of the skater melts the immediate layer of ice under his footpads. So he slips. It is an example for regalation.

12.    Why umbrellas are black?

Black is the best absorber of heat. That is why under umbrella it is cool.

13.    Cloudy night is hotter than clear night. Why?

The clouds donot allow heat going into space. That is why it is hot.

14.    Children born on top of hilly areas have big heads. Why?

On top of mountains air indirectly oxygen is very less. To supply more oxygen to brain it struggles a lot. That is why the size of the head increases.

15.    It is very dangerous to eat non-veg. farm animals, fowls… why?

To get more yield antibiotics are given. This increases flesh but at the same time the microorganisms get high resistance. They enter our body causing diseases.

The cut and displayed flesh attracts lot of bacteria and virus which enter our body.

All these directly disturb our digestive system.

16.    The sun’s rise is not same on all the days. Why?

There are many reasons for this.

The speed of the earth in the orbit around the sun.

The bending  in its axis.

The revolution is in elliptical orbit.

In elliptical revolution some  times it is near to sun and some times it is far way from sun.

As the distance differs the light takes different time to reach earth.

17.    Heart attacks. Why?

There are some reasons.

Those who eat fat contents more,

Those who smoke,

Age factor,

More oil foods,

Milkshakes,

18.      What is time?

The angle of sun’s ray is called time.

19.      What  is snow ?

Snow is the solid form of carbon dioxide.

20.      Why is time different at different places?

The earth is round. The sun rays fall at different places at different angles. That is why different places have different timings.

21.      Ordinary glasses when used for boiling breaks. Why?

Ordinary glassware is made up of silicon only. Silicon is a bad conductor of heat. Heat spreads unevenly through different layers. This uneven expansion and contraction leads to breaking of the glass.

22.      Why the height of the Himalayas is rising?

Once there was a sea where the present Himalayas lie,. Because of continental drift theory India is pushing into Asia. Asia does not move. So because of this push, the soil rises. That is why the height of Himalayas rise always.

23.      What is continental drift theory?

All the continents of the world are floating pieces on magma. Because of earth’s rotation at 1600 kmph the magma too rotates. The floating pieces rotate and drift. This is called continental drift theory.

24.      Are there extra terrestrial beings?

There are 30,000 stars similar to our Sun in our Milkyway galaxy. As sun has one planet having life the scientists too believe that there may be life on the other planets too. The probability is at least three civilisations in our Milkyway Galaxy itself.

25.       What is geocentric theory?

In ancient times people used to think that the earth was flat.

Later they thought that the earth was flat and the centre of the universe. The sun was eaten by a demon during night and by day it used to leave the sun in the east.

If people go to the edge of the earth they would fall down.

Ptolemy said that the earth flat and the centre of the universe. For 1600 hundred years no body questioned or challenged him.

Earth centred universe is called geocentric theory.