A refrigerator has a coefficient of performance of 4 . If the refrigerator absorbs 30 cal of heat from the cold reservoir in each cycle, the heat expelled (in cal) into the heat reservoir is
a. 40.5
b. 37.5
c. 36.5
d. 34.5
e. 22.5
b
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Derive an equation for the net rate of radiant heat transfer from surface 1 in the system shown in the accompanying sketch. Assume that each surface is at a uniform temperature and that the geometrical shape factor F1–2 is 0.1.
IVEN
• The system shown above
FIND
• An expression for the net rate of radiant heat transfer from surface 1 (q1) ASSUMPTIONS
• Steady state
• A1 and A2 are gray, A0 is black
• Each surface is at a uniform temperature
• The shape factor F12 = 0.1
PROPERTIES AND CONSTANTS
he Stephan-Boltzmann constant (?) = 5.67× 10–8 W/(m2 K4)
A 10-kg rock and a 20-kg rock are thrown upward with the same initial speed v0 and experience no significant air resistance. If the 10-kg rock reaches a maximum height h, what maximum height will the 20-kg ball reach?
A) h/4 B) h/2 C) 2h D) h E) 4h
Water flows through a pipe having a varying width. More water flows per second through the wide section than through the narrow section because there is more room for it to flow
A) True B) False
A baseball has mass 143 g and a speed of 45 m/s, with the speed known to within 0.10%
What is the minimum uncertainty in the position of the baseball? (h = 6.626 × 10-34 J ? s) A) 1.4 × 10-30 m B) 1.8 nm C) 1.4 × 10-32 m D) 1.6 × 10-32 m E) 1.6 × 10-30 m