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Q. A circular plate, a cube and a sphere, all made up of same material and having the same
mass, are heated to 300°C and left in a room. Which of them will have the slowest rate of cooling?

  • (A) Circular plate
  • (B) Cube
  • (C) Sphere
  • (D) All will cool at the same rate
  • Correct Answer - Option(C)
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  • Filed under category Physics
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Explanation by: Admin
In the late of 17th century British scientist Isaac Newton studied cooling of bodies. Experiments showed that the cooling rate is approximately proportional to the difference of temperatures between the heated body and the environment. This fact can be written as the differential relation : dQ dt A T T S= abg, where A is the surface area of the body through which the heat is transferred, T is the temperature of the body, TS is the temperature of the surrounding environment, á is the heat transfer coefficient depending on the geometry of the body, state of the surface, heat transfer mode, and other factors. Surface area or volume ratio is an important influence on temperature control. For same volume sphere has minimum surface area, while circular plate has maximum surface area. So sphere cools slowest and plate cools fastest.

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