Q149 / 150 · MHT CET 2026 (13 April Shift 1) · Physics
A celsius and a Fahrenheit thermometer are dipped in boiling water. The temperature of water is lowered until the Farenheit thermometer shows $140^\circ$. What is the fall in temperature on the Celsius thermometer?
- A$60^\circ$ C
- Correct answerB$40^\circ$ C
- C$50^\circ$ C
- D$80^\circ$ C
Solution
The initial temperature of boiling water is $100^\circ$ C, which corresponds to $212^\circ$ F.
The final temperature is given as $140^\circ$ F.
The relationship between the Celsius and Fahrenheit scales is given by:
$\dfrac{C}{5} = \dfrac{F - 32}{9}$
Substituting $F = 140$:
$\dfrac{C}{5} = \dfrac{140 - 32}{9} = \dfrac{108}{9} = 12$
$C = 60^\circ$ C
The fall in temperature on the Celsius thermometer is the difference between the initial and final temperatures:
$\Delta C = 100^\circ \text{ C} - 60^\circ \text{ C} = 40^\circ \text{ C}$
Answer: $40^\circ$ C
The final temperature is given as $140^\circ$ F.
The relationship between the Celsius and Fahrenheit scales is given by:
$\dfrac{C}{5} = \dfrac{F - 32}{9}$
Substituting $F = 140$:
$\dfrac{C}{5} = \dfrac{140 - 32}{9} = \dfrac{108}{9} = 12$
$C = 60^\circ$ C
The fall in temperature on the Celsius thermometer is the difference between the initial and final temperatures:
$\Delta C = 100^\circ \text{ C} - 60^\circ \text{ C} = 40^\circ \text{ C}$
Answer: $40^\circ$ C
Hence, the correct answer is option: 'B'.