Newton’s law of cooling establishes a relationship between the temperature of a substance and the time taken by the object to cool down. It states that the rate of loss of heat from a body is proportional to the difference in the temperature of the body and the surroundings. For the best results, the temperature change must be small and the nature of the heat transfer mechanism must not vary. It was published by Sir Issac Newton during the early 17th century. There are certain limitations to Newton’s law of cooling such as the temperature of the surroundings is required to be constant throughout the observation time and the mode of heat loss from the body must be only in the form of radiations.
Examples of Newton’s Law of Cooling
1. Forensic Science
One of the major application of Newton’s law of cooling can be easily seen in forensic science. The detectives and forensic scientists note down the temperature of the dead body and the room temperature of the crime scene. The temperature values are put in the mathematical formula derived by Newton’s law of cooling and the time of the victim’s death can be effectively calculated.
2. Chilled Soda Can
When we store a soda can in the refrigerator, it gets chilled. On extracting this cold can out and subjecting it to the normal room temperature, it begins to attain the ambient temperature. The temperature of the can and the surroundings is well known and recorded hence, by substituting the values in the mathematical form of Newton’s law of cooling, the rate at which the room temperature is achieved by the soda can is easily determined.
3. Cooling Down of Hot beverages
The time taken by a hot beverage to cool down is easy to calculate with the help of Newton’s law of cooling. It must be observed that a hot beverage cools down quickly during the first few minutes of exposure to room temperature. This is because at that particular instant the difference between the temperature of the beverage and the environment is significantly large hence, the time of cooling is proportional to it. Similarly, as the temperature difference goes low, the rate of cooling reduces accordingly. Hence, calculating the time taken by hot beverages to cool down is a prominent example of Newton’s law of cooling.
4. Hot and Cold Liquid kept at Ambient Temperature
Newton’s law of cooling is also helpful in determining the rate at which a liquid reaches ambient temperature. When a hot liquid and a cold liquid beverage is subjected to room temperature, it can be easily observed that the hot drink quickly attains room temperature; whereas, the cold drink takes a much longer time to reach the ambient temperature. This is because the difference between the temperature of the surrounding and the drink is proportional to the time taken by it to acquire room temperature. Hence, in such a case, the application of Newton’s law of cooling is easy to observe.
5. Measuring Temperature of a Heated Metal
Consider that a blacksmith heats a piece of metal to a considerably high temperature. When he attempts to note down the temperature of the heated metal, he finds that the measuring device or the thermometer is not capable of displaying such high-temperature values. Therefore, in such cases, the blacksmith can employ Newton’s law of cooling to measure the time taken for the metal to cool down. Thereby, estimating the original temperature of the block of metal.
6. Melting Ice-Cream
When ice cream is taken out of the freezer, it begins to melt down. The time with which it melts can not be calculated without applying Newton’s law of cooling. Provided that the difference between the temperature of the ice cream and the temperature of the surrounding is known, the rate at which it melts down can be easily calculated. This helps the ice cream vendors and distributors to calculate the adequate temperature and properly arrange the storing facilities for their product.