A solid sphere cools at the rate of `2.8^(@)C` per minute, when its temperature is `127^(@)C`. Find the rate at which another solid copper sphere of twice the radius looses its temperature at `127^(@)C`, in both the cases, the room temperature is maintained at `27^(@)C` is

Options

A. `9.72^(@)C//`min
B. `11.2^(@)C`/min
C. `3.6^(@)C`/min
D. `1.4^(@)C`/min

Answer

B

Explanation

`(R_(2))/(R_(1))=(A_(2))/(A_(1))((T_(2)^(4)-T_(0)^(4)))/((T_(1)^(4)-T_(0)^(4)))=(4r_(1)^(2))/(r_(1)^(2))=4`
`R_(2)=4R_(1)`
`=4xx2.8`
`=11.2` c/min.