Along copper rod of diameter 2.0 cm is initially at a uniform temperature of 100°c. it is now exposed to an air stream at 20°c with a heat transfer coefficient of 200 w/m2·k. how long would it take for the copper road to cool to an average temperature of 25°c?

t = 4.0 min

Explanation:

given data:

diameter of rod = 2 cm

T_1 = 100 degree celcius

Air stream temperature =  20 degree celcius

heat transfer coefficient = 200 W/m2. K

WE KNOW THAT

copper thermal conductivity = k = 401 W/m °C

copper specific heat Cp = 385 J/kg.°C

density of copper = 8933 kg/m3

charateristic length is given as Lc

Biot number is given as

Bi = 0.0025

As Bi is greater than 0.1 therefore lumped system analysis is applicable

so we have

............1

where b is given as

b = 0.01163 s^{-1}

putting value in equation 1

solving for t we get

t = 4.0 min

energy can be converted from one form to another, but it cannot be created or destroyed in ordinary chemical or physical means. do not understand what you are asking but hope this

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it