Respuesta :
The spoon to transfer 40 J of energy to your hand is descibed as follows
Explanation:
Given  area of cross section of copper spoon is A = 20mm into 1.5 mm
temperature difference is DT = (100 minus 35) = 65 0C
length of the spoon is l = 18 cm,
amount of heat should be transfer Q = 40 J
coefficient of thermal conductivity of copper k = 400 W by mk
we know that the thermal conductivity is Q by t = k into A into DT by l
t = Q into l by k into A into DT
t = (40 into 0.18) by  [tex]\left(400 \times 30 \times 10^{-6} \times 65\right)[/tex]
t = 9.23 s
It takes 9.23 seconds to transfer 40 J of energy from copper spoon to hand.
The time can be calculated by the thermal conductivity formula,
[tex]\bold {\dfrac Q{t} = \dfrac {k\times A\times \Delta T} L}[/tex]
Where,
Q - amount of heat energy transferred = 40 J
A - cross section area of copper spoon = 20 x 1.5 = 30mm
k - thermal conductivity coefficient of copper = 400 W /mK
L - length of spoon = 18 cm,
[tex]\bold {\Delta T}[/tex]- temperature difference = 100-35 = 65[tex]\bold {^oC}[/tex]
put the values in the formula, and solve it for t,
[tex]\bold {\dfrac {40}{t} = \dfrac {400\times30 \times65 } {18}}\\\\\bold {t = 9.23\ sec}[/tex]
Therefore, it takes 9.23 seconds to transfer 40 J of energy from copper spoon to hand.
To know more about  thermal conductivity,
https://brainly.com/question/7643131
