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2 answers:
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Answer:
The amount of energy required is
Explanation:
The energy required to convert the ice to steam is the sum of:
1) Energy required to raise the temperature of the ice from -20 to 0 degree Celsius.
2) Latent heat required to convert the ice into water.
3) Energy required to raise the temperature of water from 0 degrees to 100 degrees
4) Latent heat required to convert the water at 100 degrees to steam.
The amount of energy required in each process is as under
1)
where
' is specific heat of ice =
2) Amount of heat required in phase 2 equals
3) The amount of heat required to raise the temperature of water from 0 to 100 degrees centigrade equals
where
' is specific heat of water=
4) Amount of heat required in phase 4 equals
Thus the total heat required equals
Answer:
far from the speaker the intensity drops to 85 dB.
Explanation:
In the equation for the Decibel scale
The ratio of the intensities can be written as
And since
and
,
meaning
Putting this into equation (1), we get:
Now, if the intensity is 100 dB when the distance is 5 meters, we have:
by taking both sides to the exponent:
Now equation (2) becomes
when the intensity level is 85 dB we have
take both sides to exponents and we get:
Thus, far from the speaker the intensity drops to 85 dB.