Question

12. During an eating contest, Sonya eats thirty-six candy bars in 10.0min, where each candy bar has 260.0 kcal (i.e. nutritional calories). The surface area of her skin is 1.25m2 and the emissivity of her skin is 0.75. Assume her skin temperature is a constant 36.0°C while metabolizing the candy bars. i. How long would it take her to emit the net radiant energy equal to the energy ingested in the candy bars? Assume she is in a 20.0°C room. ii. Instead of radiating this ingested energy, what if she were to sweat it away? How much water would she need to evaporate in a 24.0 hour period to release this energy?

Answer 1

x

12 of candy bass = 36 Given data- number energy of I candy bar = 260 kcal =(260 x103 x 4.184) J Surface area of Skin, A= 1.25m² emistivity € = 0.75 Temperature of skin, Ts = 36°C Tenperature of ambient, Ta = 20c = 20+273-15 = 293115K : 36+ 273.15–309.15K : 0 As we know- Pradiation GEACT84 - Tat) where, o= 5.76X10-8 w/ m2 kA emissivity A = Area through which radiation takes place. Temperature in Kelvin. E = I Pradiation = 5:46x158 x 0.45X 125[(309-15)4- (293.153# Pradiation 94-5 Walts Now, 14.5 xt 36 x 260 x103 x 4.184) t: 414415. 24 seconds to 115. 115 Ho of leturs consider, m= mass water energy required to evaporate water, in 24hr- ML → 36x260 x103 x 4.184 = mx 2.26x106 m = 171328 328 kg