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10 Important
Science Questions And Their Scientific Reasons.
1. Why does a
gun recoil when a shot is fired out?
Since the mass of
the gun is much greater than that of the bullet; hence the speed of the gun is
very small as compared to that of the bullet. Therefore, the gun moves
backwards only by a small distance during recoil.
2. Why are
passengers thrown in the forward direction when a running bus stops suddenly?
Passengers
sitting or standing in a running bus share the motion of the bus. This means, the
passengers in a running bus are also moving with the same speed in the same
direction. When the running bus stops suddenly, the lower part of the
passenger’s body come to rest, while the upper part continues to remain in
motion. As a result, the passengers are thrown in the forward direction when a
running bus stops suddenly.
3. An iron
ball sinks, a ship does not, why?
In case of iron ball,
its weight is more than the weight of water it displaces. In case of ships, the
space inside being vacant, the weight of the ship is less than the weight of
water it displaced. thus, whereas upward thrust is sufficient to balance the
weight of the ship, it is inadequate to balance the weight of the ball.
4. Why is
driving on a icy highway extremely dangerous?
For safe driving
frictional force between the tyres and the road is an essential factor. When
these frictional forces become less, the driving becomes difficult. As the
force of friction between the tyre and ice is very small, therefore, driving on
icy highway on icy highway becomes dangerous.
5. Why is a
gap left at the joint between two rails?
A long railway
track consists of many sections of steel called rails – joined to each other.
While laying a railway line a small gap is left in between two rails at their
joint to allow for the expansion during summer. If such a gap is not left at
the joints of rails, the track will get deformed due to thermal expansion in
summer, which may cause derailment of trains.
Another method of allowing for the
expansion of rails is to use a wedge joint between the two rails. When the
temperature rises during summer, the rails expand and their ends side part each
other.
6. Why does
water get cooled in an earthen pot (surahi or matka)?
As earthen pot
has small pores in its walls. When water is poured into it, some of it seeps
through these pores to its outer surface. On reaching there, it evaporates. The
heat required for evaporation is taken from the earthen pot and from the water
in it. As a result, the water in an earthen pot gets cooled down.
7. Explain how
bats use ultrasound to catch a prey.
Bats are usually
active at night. They search out for their prey at night. They try to detect
the ultrasonic waves emitted by them. The high pitched ultrasonic squeaks of
the bat are reflected from the obstacle or the prey and returned to bat’s ear.
The nature of reflection tells the bat about the location and size of the prey
and they are able to easily attack them.
8. Why do
diamonds shine at night?
The rays of light
entering it get internally reflected from most of the faces, on account of high
refractive index so, from a few faces that permit light to get out, a lot of
light comes out.
9. Why does a
straight stick look bent when partly immersed in water?
When the rays of
light enter another medium, they change their path due to refraction, so the
stick looks bent, when partly immersed in water.
10. Why does
it take some time to see objects in a dim room when you enter the room from
bright sunlight outside?
In a dark room,
if we try to see objects, the pupil will enlarge itself. So that more light
enters it. If one suddenly goes into bright sunlight (or switches the bright
light) one feels the glare. This is because too much light enters the enlarged
pupil. Generally, the pupil contracts and things begin to appear normally.
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