A
chef, awaking one morning to find the stove out of order decides to
boil water for coffee by shaking it in a thermos flask. Let us
suppose that the chef uses
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Solution: Click For PDF Version
We first
calculate the temperature equivalent in Celsius to
We find that
Volume of water to be boiled by shaking is
Mass of the water to be boiled is
as the
density of water
Amount of
energy gained by the water to be boiled in each shake will be the
change in gravitational potential energy in 0.35 m. It is
Specific heat
of water,
Amount of
heat required to raise the temperature of water from
As 30 shakes are imparted in a minute, the time required for obtaining mechanical energy equal to Q will be
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of
tap water at
,
and the water falls 35
cm each shake, the shape making
30 shakes each minute. Neglecting any loss of
energy, we have to estimate how long the flask must be shaken before
the water boils.
to
will be
