Q43. Suppose you are outside your home and an earthquake
strikes. What precaution would you take to protect yourself?
Ans. If we are outside our home and an earthquake
We should try to find a clear spot, away
from buildings, trees and overhead power lines. Drop to the ground.
If we are in a car or a bus, we should not
come out. We should ask the driver to drive slowly to a clear spot. We should
not come out till the tremors stop.
Q44. Name the scale on which the destructive energy of an
earthquake is measured. An earthquake measures 3 on this scale. Would it be
recorded by a seismograph? Is it likely to cause much damage?
Ans. The destructive energy of an earthquake is
measured by Richter scale. An earthquake of 3 Richter can be recorded by a
seismograph. An earthquake of magnitude 3 on Richter scale is often felt but
not likely to cause much damage. Really destructive earthquakes have magnitudes
higher than 7 on the Richter scale.
Q45. What precautions would you take to protect yourself during
an earthquake if you are at home?
Ans. In order to protect ourselves during an
earthquake we must take following precautions:
We should take shelter under a table and
stay there till shaking stops.
We should stay away from tall and heavy
objects that may fall on us.
If we are in bed then we should not get up
and should protect our head with a pillow.
Q46. Suggest three measures to protect ourselves from lightning.
Measures to protect ourselves from lightning
A house or a building is a safe place. If
we are travelling by car or by bus, we are safe inside with windows and doors
of the vehicle shut.
Lightning can strike telephone cords,
electrical wires and metal pipes. During a thunderstorm when lightning is
taking place, contact with these should be avoided.
Carrying umbrella is not a good idea at all
during lighting because lightning may strike the top end of the metal rod of
umbrella and harm us.
Q47. What causes an earthquake?
Ans. Causes of an earthquake
The outermost layer of the earth is not in
one piece. It is fragmented. Each fragment is called a plate. These plates are
in continual motion. When they brush past one another, or a plate goes under
another due to collision, they cause disturbance in the earth’s crust. It is
this disturbance that shows up as an earthquake on the surface of the earth.
Tremors on the earth can also be caused
when a volcano erupts, or a meteor hits the earth, or an underground nuclear
explosion is carried out.
Q48. What causes lightning in the sky?
Ans. During the development of a thunderstorm, the air
currents move upward while the water droplets move downward. These vigorous
movements cause separation of charges. The positive charges collect near the
upper edges of the clouds and the negative charges accumulate near the lower
edges. There is accumulation of positive charges near the ground also. When the
magnitude of the accumulated charges becomes very large, the air which is
normally a poor conductor of electricity is no longer able to resist their
flow. Negative and positive charges meet, producing streaks of bright light and
sound. We see streaks as lightning. The process is called an electric
Q49. State some precautions that people should take to protect themselves
against earthquakes if they live in seismic zones of the country.
Ans. People living in seismic zones should take the
following measures for protection against earthquakes:
All the buildings in these zones should be
designed so that they can withstand major tremors. Modern building technology
can make it possible.
In highly seismic areas, the use of mud or
timber is better than the heavy construction material. Keep roofs as light as
possible. In case the structure falls, the damage will not be heavy.
It is better if the cupboards and shelves
are fixed to the walls, so that they do not fall easily.
Wall clocks, photo-frames, water heaters
etc., should be mounted securely on the walls, so that in the event of an
earthquake, they do not fall on people.
Since some buildings may catch fire due to
an earthquake, it is necessary that all buildings, especially tall buildings,
have fire fighting equipment in working order.