| Q: How do solar calculators work? |
| Answer: The claculators of today use miniature electronic circuits to
carry out calculations. These circuits are normally provided with
electricity from battery cells. In a solar calculator, the electricity
is obtained from sunlight through photovoltic cells. These cells have
thin slices of semiconductors. The surface facing the light gets
positively charged and the other surface becomes negatively charged.
Thus they make up the battery terminals for the flow of electricity. |
| Q: Why does an iron ball sink but not an iron ship? |
| Answer: Any object kept in a fluid, is subject to an upward force or
pressure, that is the buoyancy force exerted by the fluid. The famous
greek scientist, Archimedes, discovered that this force is equal to the
wieght of the volume of the fluid displaced by the object. If the weight
of the object is more than the weight of the water displaced, it sinks
into the water. If both these weights are equal, the objects floats in
an immersed position. However, if the weight of the object is less than
the weight of the water it displaces, the object is pushed up above the
surface of the water till weight of the water displaced by the portion
of the object remaining below the surface equals the weight of the
object. Following this principle, the bottom portion of the ship is made
hollow so that it can displace a large volume of water, so large that
the weight of the water displaced is equals the weight of the ship along
with its load. A solid iron ball sinks but a hollow iron ball of equal
size. i.e. having the same volume but less weight may float. |
| Q: Why do we use two sails in a sail boat? |
| Answer: In order to move in our desired direction, we use two sails in
a sail boat. One sail is used to catch the wind and reflect on the
other. The other sail is faced to our desired direction with the aid of
an instrument called
Rudder. When the wind falls on the other sail (which is facing
towards the desired direction), it exerts pressure on the other sail.
Due to this pressure the boat proples in the desired direction. |
| Q: How do we get photos from negatives ? |
| Answer: When a photograph is to be printed the negative image is first
made into positive image. This is done by pressing the negative tightly
on a paper which has silver salts. These slats turn black on exposure to
light. When light is passed through the negative to this paper a
chemical change takes place on the paper. The light areas of the
negative will transmit more light than the dark areas of the negative.
The negative image is reversed on the paper, which is then fixed using a
solution, usually sodium thiosulphate. This washes away the unexposed
silver salts on the paper. After washing with water and then drying it,
the photograph is ready. |
| Q: How does thermos flask keep a hot drink hot and a cold one
cold? |
| Answer: A thermos flask is basically a double container where space
between the walls is kept under vaccum and outer surface of the walls
are kept shiny and smooth so that they act like mirrors. The vaccum
prevents the flow of heat through the walls by conducton or convection,
the process which require some medium. Heat transfer by radiation can
take place through the vaccum, but the radiation heat is reflected back
by the mirrored surfaces. So, not much heat can flow throught the walls
of the flask and your drink remains hot or cold as desired. |
| Q: Why does the heart beat faster ? |
| Answer: The heart beat faster during and after exercise. This is
because during exercise the amount of carbon dioxide in the blood
increases. To take the carbon dioxide out of the body the rate of
breathing increases. Simultaneously the heart beat increases to speed up
the circulation so that the blood can carry carbon dioxide out and bring
in oxygen at faster rate. |
| Q: How Does Artificial gravity Work? |
| Answer: Spinning creates centripetal force, which increases with faster
spin rates. A popular amusement park ride consists of a cylinder that
spins around a vertical axis. People stand with their backs to the
inside wall and the cylinder spins up. Once it's going fast enough, the
floor drops away and everyone is stuck to the wall by the artificial
gravity. What's really happening is that the cylinder wall is exerting a
force (centripetal force) to keep everyone moving on a curved path (in
this case, a circular path). But to the people or any other object in
the cylinder, the effect is the same as if there were a force pushing
them outward (called the centrifugal force) -- that's the artificial
gravity. |
| Q: Why does the gun recoils? |
| Answer: When a bullet is fired from a gun, the force sending the
bullet forward is equal to the force sending the gun backward. But due
to high mass of the gun, it moves only a little distance backward and
gives a backward jerk or kick to the shoulder of the gunman. The gun is
said to have recoiled |
| Q: How does a blanket that keeps us warm in winter also keep ice
from melting ? |
| Answer: A blanket and similar woolen garments are bad conductors of
heat. This means they do not allow heat to be transferred easily. When
you wrap yourself in a blanket in cold weather, the blanket prevents
your body from shedding its own warmth. So you feel warm and snug inside
a coat or a blanket. However, if you keep ice inside a coat or a
blanket, the blanket blocks the warm air outside from coming in and
causing the ice to melt. |
| Q: How Do we Walk? |
| Answer: When we walk on the ground our foot pushes the ground
backward, and in return, the ground pushes our foot forward. The forward
reaction exerted by the ground pushes our foot forward. The forward
reaction exerted by the ground on our foot makes us walk forward. if
however the ground is slippery or if there is all ice, it becomes very
difficult to walk. This due to the fact that on the slippery ground or
ice, The friction is much less, and we cannot exert a backward action
force on a slippery ground or ice which would produce a forward reaction
force on us |
| Q: Why the gun recoils? |
| Answer: When a bullet is fired from a gun, the force sending the
bullet forward is equal to the force sending the gun backward. But due
to the high mass of the gun, it moves only a little distance backward
and gives a backward jerk or kick to the shoulder of the gunman. The gun
is said to have recoiled. |
| Q: How does compass point at north - south Direction ? |
| Answer: Earth behaves like a magnet with its own north - south Poles .
But its North Pole is near geographic South pole (The South Pole we
predict) and its South Pole near geographic North Pole (The North Pole
we predict) . As you know like poles of two different magnet attract .
So when the compass's (which is also a magnet ) north pole attract the
south pole of the Earth (which is near geographic north pole) , the
compass indicate geographic North Pole . This applies same on the case
of pointing at the south pole . 
|
| Q: Why in some planes we hear the sound of the plane after we
see it ? |
| Answer: There mostly two types of planes - SONIC and SUB SONIC planes
. Sub sonic planes have the speed less than sound whereas the Sonic
planes are those which are faster than sound . so in sonic planes we
hear the sound after we see it because it it is faster than sound .
|
| Q: Why don't submarine sink when they move under water ?
|
| Answer: When a submarine is moving on the surface of water it is kept
afloat by the air which is stored in its blast tanks . In order to go
underwater these tanks are filled with water . This increases the
density of the ship . According to the law of buoyancy the
float inside water when the wieght of the body equal to the wieght of
the water displayed by it. Therefore tanks are filled till the submarine
niether rises nor sinks , but stays at the required depth .
|
| Q: Why do we feel warm when we run or exercise ? |
| Answer: The human body is like a machine which transforms energy . The
body changes energy from food into other kinds of energy . One form of
energy is called Dynamic Energy . This is developed in the
muscles . When the muscles are used in exercise or running , part of
energy is turned into heat - thermal energy . If you run
very fast more heat is produced . This is why you feel warm when you
have been playing games or running races .
|
| Q: What makes a parachute land slowly? |
| Answer: Like water ,air also exerts a Buoyancy force on
a body trying to come down through it . When the parachute is spread ,
the Buoyancy force becomes very high and almost balances the weight of
parachute and Parachuter together and the parachute descends slowly
through the air . |
| Q: What keeps a satellite in Orbit? |
| Answer: Its great speed. Satellite in low orbits travel at an
incredible 17,500 miles or 27,350 Kilometers an hour ! But at the same
time while they are moving forward , gravity is pulling them down . The
combined motion - forward and downward - keeps the satellite in orbit .
It remains at a safe altitude above EARTH - and does not even need
engines to stay up . |
| Q: How is it that our weight decreases on moon ? |
| Answer: Our weight is due to the force exerted by EARTH on us - the
force of gravity . The MOON has one-sixth the gravity of the earth and
so our weight on moon is one sixth our weight on the earth. So if you
are 42 Kg on EARTH , you will weigh just 7 Kg on the MOON. |
| Q: When any meteor or object enters the atmosphere, it burns
whereas a man made space shuttle or rocket does not burn . Why ?
|
| Answer: When any meteor enters the earth's atmosphere, its friction or
rubbing with the air makes it heat up to such an extent that it burns
and we see a
shooting star. On the contrary a man made rocket or space shuttle is
protected by a thick heat shield which can withstand very high
temperatures and thus they do not burn. This shield is made of heat
resistant tiles. If there were no shield, the rocket or the space
shuttle would burn up, just like a meteor .
|
