Question

Imagine that a black lead ball of mass 30 kg is shot out of a cannon and thereby its temperature rises to 80 Celsius.  What is the initial power radiated from the ball?  How long will it take the ball to cool back down to 27 Celsius if the outside air temperature is 26 Celsius?  [Assume that it radiates away its heat like a perfect black body with e = 1 and its radius is 20 cm, but the air temperature remains constant, and ignore any conduction between the lead and the air.] C_lead = 128 J/kg.

a) 96.57 min

b) 63.67 min

c) 78.48 min

d) 87.22 min

e) 71.58 min

Answer 1