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Q. No.A body takes \(4 ~\text{min}\) to cool from \( 61^\circ \text C\) to \( 59^\circ \text C.\) If the temperature of the surroundings is \( 30^\circ \text C,\) the time taken by the body to cool from \( 51^\circ \text C\) to \( 49^\circ \text C\) is:
1. \(6~\text{min}\)
2. \(3~\text{min}\)
3. \(4~\text{min}\)
4. \(8~\text{min}\)
1. \(6~\text{min}\)
2. \(3~\text{min}\)
3. \(4~\text{min}\)
4. \(8~\text{min}\)
Subtopic: Â Newton's Law of Cooling |
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Level 1: 80%+
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A pan filled with hot food cools from \(95^\circ\text{C}\) to \(85^\circ\text{C}\) in \(2\) minutes when the room temperature is \(20^\circ\text{C}.\) The time taken by the food to cool from \(55^\circ\text{C}\) to \(45^\circ\text{C}\) will be:
1. \(260~\text s\)
2. \(280~\text s\)
3. \(300~\text s\)
4. \(320~\text s\)
1. \(260~\text s\)
2. \(280~\text s\)
3. \(300~\text s\)
4. \(320~\text s\)
Subtopic: Â Newton's Law of Cooling |
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A body cools from \(62^{\circ}\text{C}\) to \(50^{\circ}\text{C}\) in \(10\) min and to \(42^{\circ}\text{C}\) in the next \(10\) min. The temperature of the surrounding is:
1. \(16^{\circ}\text{C}\)
2. \(26^{\circ}\text{C}\)
3. \(36^{\circ}\text{C}\)
4. \(21^{\circ}\text{C}\)
1. \(16^{\circ}\text{C}\)
2. \(26^{\circ}\text{C}\)
3. \(36^{\circ}\text{C}\)
4. \(21^{\circ}\text{C}\)
Subtopic: Â Newton's Law of Cooling |
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Level 1: 80%+
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A pan filled with hot food cools from \(95^\circ \text{C}\) to \(85^\circ \text{C}\) in \(2\) min when the room temperature is \(20^\circ \text{C}.\) The time taken by the food to cool from \(55^\circ \text{C}\) to \(45^\circ \text{C}\) will be:
| 1. | \(260\) s | 2. | \(280\) s |
| 3. | \(300\) s | 4. | \(320\) s |
Subtopic: Â Newton's Law of Cooling |
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A body cools down from \(65^\circ \text{C}\) to \(60^\circ \text{C}\) in \(5\) minutes. It will cool down from \(60^\circ \text{C}\) to \(55^\circ \text{C}\) in:
| 1. | \(5\) minutes |
| 2. | less than \(5\) minutes |
| 3. | more than \(5\) minutes |
| 4. | less than or more than \(5\) minutes depending on whether its mass is more than or less than \(1~\text{kg}\) |
Subtopic: Â Newton's Law of Cooling |
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Hints
An object cools down from \(80^\circ \text{C}\) to \(60^\circ \text{C}\) in \(5\) min in a surrounding of temperature \(20^\circ \text{C}.\) The time taken to cool from \(60^\circ \text{C}\) to \(40^\circ \text{C}\) will be:
(Assume Newton's law of cooling to be valid.)
(Assume Newton's law of cooling to be valid.)
| 1. | \({ 25 \over 3} ~\text {min}\) | 2. | \(5 ~\text {min}\) |
| 3. | \({ 25 \over 4} ~\text {min}\) | 4. | \(9~ \text {min}\) |
Subtopic: Â Newton's Law of Cooling |
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JEE
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A certain quantity of water cools from \(70~^{\circ}\text{C}\) to \(60~^{\circ}\text{C}\) in the first \(5\) minutes and to \(54~^{\circ}\text{C}\) in the next \(5\) minutes. The temperature of the surroundings is:
1. \(45~^{\circ}\text{C}\)
2. \(20~^{\circ}\text{C}\)
3. \(42~^{\circ}\text{C}\)
4. \(10~^{\circ}\text{C}\)
Subtopic: Â Newton's Law of Cooling |
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Level 2: 60%+
AIPMT - 2014
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A piece of metal is heated to a temperature \(T_{2}\) and then allowed to cool in a room which is at temperature \(T_{1}.\) The graph between the temperature \(T\) of the metal and time \(t\) will be close to:
| 1. |  |
2. |  |
| 3. |  |
4. |  |
Subtopic: Â Newton's Law of Cooling |
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A metallic block having a thermal capacity of \(30~\text{cal}/^\circ\text C\) is placed in a room at \(20^\circ\text C.\) When the temperature of the block is \(30^\circ\text C,\) it is observed to cool down at a rate of \(0.6^\circ\text C\) per min. Assume that Newton's law of cooling applies.
If the temperature of the block is \(40^\circ\text C,\) other things remaining unchanged, the rate of cooling will be
1. \(0.3^\circ\text C/\text{min}\)
2. \(0.8^\circ\text C/\text{min}\)
3. \(1.2^\circ\text C/\text{min}\)
4. \(2.4^\circ\text C/\text{min}\)
If the temperature of the block is \(40^\circ\text C,\) other things remaining unchanged, the rate of cooling will be
1. \(0.3^\circ\text C/\text{min}\)
2. \(0.8^\circ\text C/\text{min}\)
3. \(1.2^\circ\text C/\text{min}\)
4. \(2.4^\circ\text C/\text{min}\)
Subtopic: Â Newton's Law of Cooling |
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Level 2: 60%+
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