Aclosed box is filled with dry ice at a temperature of -87.1°c, while the outside temperature is 17.6°c. the box is cubical, measuring 0.332 m on a side, and the thickness of the walls is 4.41 × 10^-2 m. in one day, 3.34 × 10^6 j of heat is conducted through the six walls. find the thermal conductivity of the material from which the box is made.

K=24.17 x 10⁻² J s⁻¹c⁻¹m⁻¹

Explanation:

Rate of flow of heat through a material is given by the following expression

where Q is amount of heat flowing in time t through area A and  a medium of thickness d having two faces at temperature difference δT . K is thermal conductivity of the medium .

Here Q = 3.34 x 10⁶/6 , t = 24 x 60 x 60 = 86400 s , A = .332 X .332 = .0110224 m² ,  δT = 104.7

Put these values here

K=24.17 x 10⁻² J s⁻¹c⁻¹m⁻¹

To solve this exercise, the following speed equation must be applied:

 V = d / t (mi/hr)

 V: speed (mi/hr)

 d: distance (mi)

 t: time (s)

We know the distance (d= 5 miles) and the time (t= 0.2 hours), so we proceed to replace these values in the formula to calculate the lion’s speed:

 V = d / t

 V = 5 mi/0.2 hr

 V = 25 mi/hr

 The lion’s speed is 25 mi/hr, so the last option is the right answer