Published by:
CGP EDU Academic Team
Published on: September 12, 2026
From what height should a piece of ice (0°C) fall so that it melts completely? Only one-quarter of the energy produced is absorbed by the ice as heat. (Latent heat of ice = 3.4 × 10 5 J kg –1 , g = 10 m/s 2 )
Text Solution
Verified by ExpertsThe correct answer is:
A
To determine the height from which the ice should fall to melt completely, we need to consider the energy transformations involved.
Step 1: Calculate the energy required to melt the ice.
The latent heat of fusion for ice is given as \( L = 3.4 \times 10^5 \: \text{J/kg} \). If we let the mass of the ice be \( m \) kg, the total energy required to melt the ice completely can be expressed as:
\[ Q = mL = m(3.4 \times 10^5) \: \text{J} \]
Step 2: Calculate the gravitational potential energy gained by the ice when it falls from a height \( h \).
The potential energy (PE) at height \( h \) is given by:
\[ PE = mgh = mg(10)h = 10mh \]
Step 3: Set up the equation considering that only one-quarter of the energy produced is absorbed by ice:
\[ \frac{1}{4}PE = Q \]
Thus, we have:
\[ \frac{1}{4}(10mh) = m(3.4 \times 10^5) \]
Step 4: Simplify the equation:
The mass \( m \) cancels out (providing \( m \neq 0 \)):
\[ \frac{10h}{4} = 3.4 \times 10^5 \]
Step 5: Solve for height \( h \):
\[ 10h = 4 \times 3.4 \times 10^5 \]
\[ h = \frac{4 \times 3.4 \times 10^5}{10} \]
\[ h = \frac{13.6 \times 10^5}{10} = 1.36 \times 10^5 \: ext{m} = 136000 ext{ m} \]
Therefore, the height from which the ice should fall to melt completely is 136,000 m (or 136 km). Hence, the correct answer is option A.
Step 1: Calculate the energy required to melt the ice.
The latent heat of fusion for ice is given as \( L = 3.4 \times 10^5 \: \text{J/kg} \). If we let the mass of the ice be \( m \) kg, the total energy required to melt the ice completely can be expressed as:
\[ Q = mL = m(3.4 \times 10^5) \: \text{J} \]
Step 2: Calculate the gravitational potential energy gained by the ice when it falls from a height \( h \).
The potential energy (PE) at height \( h \) is given by:
\[ PE = mgh = mg(10)h = 10mh \]
Step 3: Set up the equation considering that only one-quarter of the energy produced is absorbed by ice:
\[ \frac{1}{4}PE = Q \]
Thus, we have:
\[ \frac{1}{4}(10mh) = m(3.4 \times 10^5) \]
Step 4: Simplify the equation:
The mass \( m \) cancels out (providing \( m \neq 0 \)):
\[ \frac{10h}{4} = 3.4 \times 10^5 \]
Step 5: Solve for height \( h \):
\[ 10h = 4 \times 3.4 \times 10^5 \]
\[ h = \frac{4 \times 3.4 \times 10^5}{10} \]
\[ h = \frac{13.6 \times 10^5}{10} = 1.36 \times 10^5 \: ext{m} = 136000 ext{ m} \]
Therefore, the height from which the ice should fall to melt completely is 136,000 m (or 136 km). Hence, the correct answer is option A.
Prepare Smarter with CGP Edu
Get practice questions, solutions, and test series in one place.
Write a Review
Share your experience with this question and solution.
Commentary
Send your comment, doubt, correction, or feedback to admin.
Similar Questions
Explore conceptually related problems
When vapor condenses into liquid
At NTP water boils at 100°C. Deep down the mine, water will boil at a temperature
If specific heat of a substance is infinite, it means
A gas in an airtight container is heated from 25°C to 90°C. The density of the gas will
A quantity of heat required to change the unit mass of a solid substance, from solid state to liqui…
The latent heat of vaporization of a substance is always