A cubical block of mass `1.0kg` and edge `5.0cm` is heated to `227^(@)C` . It is kept in an evacuated chamber maintained at `27^(@)C` . Assuming that the block emits radiation like a blackbody, find the rate at which the temperature of the block will decreases. Specific heat capacity of the material of the block is `400Jkg^(-1)K^(-1)` .

Answer

A, B, C

Explanation

Since the cube can be assumed as black body`
`e=1, sigma=6.0xx10^(-8)W//m^(2)-K^(4)`
`A=6xx25xx10^(-4)m^2`
`m=1 kg ,S=400j//kg-^(@)K`
`T_1=227^(@)C=500K`
`T_2=27^(@)C=300K`
`ms(d theta)/(dt)= A sigma e(T_(1)^(4)-T_(2)^(4))`
`(D theta)/(dt)=`
`(1xx6xx10^(-8)xx6xx10^(-4)[(500)^4-(300)^(4)]/(1xx400)`
`=(36xx25xx544)/(400)xx10^(-4)`
`=0.12240^(@)C//s`
`=0.120^(@)C//s.`