CSIR
-NET 2015 (Dec)
97.
A tsunami occurs 1000 km away form the shore in an ocean water depth
of 6.25km. The tsunami reaches the shore in about
a)
1hr
b)
2hr
c)
4hr
d) 8hr
Solution:
Velocity
of the Tsunami wave (V) = (√g*d) --------------------(1)
g
= acceleration due to gravity (9.8 m/s2)
d
= depth (6250 m)
V=
(√9.8 * 6250)
V=
247.48 m/s
The
Tsunami reaches the shore at time(t) = distance/ velocity
---------(2)
Distance=
1000000 m
velocity
= 247.48 m/s
time=
(1000000/ 247.48)
=
4040s
Therefore
time= 1hr 7min
Explanation:-
Tsunami:-
A
tsunami is a very long-wavelength wave of water that is generated by
sudden displacement of the sea floor or disruption of any body of
standing water. Tsunami are sometimes called "seismic sea
waves", although they can be generated by mechanisms other than
earthquakes.
Physical
Characteristics of Tsunami
All
types of waves, including tsunami, have a wavelength, a wave height,
an amplitude, a frequency or period, and a velocity.
Wavelength
is defined as the distance between two identical points on a wave
(i.e. between wave crests or wave troughs). Normal ocean waves have
wavelengths of about 100 meters. Tsunami have much longer
wavelengths, usually measured in kilometers and up to 500 kilometers.
Wave
height refers to the distance between the trough of the wave and the
crest or peak of the wave.
Wave
amplitude - refers to the height of the wave above the still water
line, usually this is equal to 1/2 the wave height. Tsunami can have
variable wave height and amplitude that depends on water depth as we
shall see in a moment
Wave
frequency or period - is the amount of time it takes for one full
wavelength to pass a stationary point.
Wave
velocity is the speed of the wave. Velocities of normal ocean waves
are about 90 km/hr while tsunami have velocities up to 950 km/hr
(about as fast as jet airplanes), and thus move much more rapidly
across ocean basins. The velocity of any wave is equal to the
wavelength divided by the wave period.
V
= λ/P
The
velocity of a shallow-water wave is also equal to the square root of
the product of the acceleration of gravity, g, (10m/sec2) and the
depth of the water, d.
v=√g*d
Reference:
http://www.tulane.edu/~sanelson/Natural_Disasters/tsunami.htm
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