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There are two spherical balls A and B of...

There are two spherical balls A and B of the same material with same surface finish but the radius of A is half than of B. If A and B are heated to the same temperature and allowed to cool then :

A

rate of cooling of both is same

B

rate of cooling of A is four times that of B

C

rate of cooling of A is twice that of B

D

rate of cooling of A is `1//4` time that of B.

Text Solution

Verified by Experts

The correct Answer is:
D
Rate of cooling `prop` area of body.
`rArr" "` rate of cooling `prop"(radius)"^(2)`.
`:.` since radius of A is `1/2` od radius of sphere B.
`:.` rate of cooling of A is `1/4` of rate of cooling of sphere B.
Thus correct choice is (d).
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