Tag: change of states

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Multiple choice physics the kinetic model of matter force and kinetic theory change of states phase change

Cooking takes longest time

  1. At the sealevel

  2. At Simla

  3. At Mount Everest

  4. In a submarine 100 m below the surface of water
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cooking takes longer at higher altitudes because the atmospheric pressure is lower, which causes water to boil at a lower temperature. Mount Everest has the lowest atmospheric pressure among the options, making it the slowest for cooking.

Multiple choice physics the kinetic model of matter force and kinetic theory change of states phase change

Normallly the body temperature of healthy person is ______ Degree celcius?

  1. 25

  2. 37

  3. 30

  4. 32
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Normally the body temperature of healthy person is $37^oC$ or ($98.6^oF$)
It is scientific fact that normal body temperature of a healthy body is $37^oC$. Apparently it is the perfect balance as it's warm enough to prevent fungal infection but not so hot that we need to eat non-stop to maintain out metabolism.
Multiple choice physics the kinetic model of matter force and kinetic theory change of states phase change

Water in a lake is changing into ice at $0^{o}C$. When the atmospheric temperature is $10^{o}C$. If the time taken for $1\ cm$ thick ice layer to be formed is $7$ hour, the time required for the thickness of ice to increase from $1\ cm $ to $2\ cm$ is

  1. $7\ hour$

  2. $14\ hour$

  3. $<7\ hour$

  4. $>14\ hour$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The rate of ice formation is proportional to the thickness already formed because the heat must conduct through the existing ice layer. If it takes 7 hours to form the first 1 cm, the next 1 cm (from 1 cm to 2 cm) takes three times the duration of the first interval in some models, but standard physics problems of this type often follow the t proportional to x^2 rule. Specifically, t1 = k(x1^2), t2 = k(x2^2 - x1^2). Here, 7 = k(1^2), so k = 7. The time for the next cm is 7(2^2 - 1^2) = 7(3) = 21 hours. Given the options, 14 hours is often cited in simplified textbooks, but mathematically it should be 21.

Multiple choice physics the kinetic model of matter force and kinetic theory change of states phase change

How much heat energy is gained when 5 kg of water at  $20 ^ { \circ } \mathrm { C }$ is brought to its boiling point?

  1. 1680 KJ

  2. 1700 KJ

  3. 1720 KJ

  4. 1740 KJ
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$Q = mc\Delta \theta $

$ = 5 \times \left( {1000 \times 4.2} \right) \times \left( {100 - 20} \right)$
$ = 1680 \times {10^3}J$
$ = 1680\,KJ$
Hence,
option $(A)$ is correct answer.