a) At what depth in water is the pressure 37.6 times the pressure at the surface
ID: 1693032 • Letter: A
Question
a) At what depth in water is the pressure 37.6 times the pressure at the surface, which is at 1 ATM ?b) Two stars radiate as black bodies(e = 1). Star A has a radius three times as large as star B but a temperature 1/3 that of star B. If star B radiates a power of PB, what is the power PA radiated by star A?
c) Suppose the heat flow rate through a wall is H. If we double all the wall dimensions (height, width, thickness) but keep the temperature difference the same, what would the new heat flow rate be?
d) A hurricane wind blows horizontally across a 10m X 12m flat roof on a house. Find the wind speed that will produce an upward force of 2x10^5 Nt on the roof.
( 1ATM = 105 Pa, k = 1.38 x 10-23 J/degK)
Explanation / Answer
a)pressure at the surface P _o = 1 ATM presssure at depth P = 37.6 ATM P = P_o + ? g h ? g h = P - P _ o h = P - P _ o / ?g = ( 37.6 - 1 )*1.03*10^ 5 N / m^2 / (1000)(9.8) = 384.6 m b) power out put by star B is P_B r_A = 3 r_B intensity of star A is I = P_A / A = s T^4 P_A = A_A s T^ 4 = ( 4p (3r_B)^2 ) (s )(T_B / 3 ) ^ 4 = 9 A_B s( T_B)^4 = 0.11 P_B c)Heat flow rate Q = k A ?T / d here A = area If we double all the wall dimensions (height, width, thickness) but keep the temperature difference the same Q' = k ( 4A ) ?T / 2 d = 2 Q d)Related Questions
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