How many joules of energy are used by a 1.0-hp motor that runs for 1.0 hour? (1 hp = 746 W)
A) 3.6 kJ
B) 2.7 MJ
C) 45 kJ
D) 4.8 J
B
You might also like to view...
The density of the universe is
a. equal to the critical density if the universe is closed. b. equal to the critical density if the universe is flat. c. greater than the critical density if the universe is flat. d. greater than the critical density if the universe is open. e. none of the above
In the operation of a steam-electric generating plant, the work output [from thermal energy to work] occurs
A) at the point where the fossil or other fuel is shipped into the plant area. B) in the condenser. C) at the point where the energy from the furnace is transferred into the boiler. D) at the point where the hot steam pushes against the turbine. E) in the electric generators.
Neptune circles the Sun at a distance of 4.50 × 1012 m once every 164 years. Saturn circles the Sun at a distance of 1.43 × 1012 m. What is the orbital period of Saturn?
A) 304 years B) 121 years C) 109 years D) 88.6 years E) 29.4 years
In the inspection of a sample of meat intended for human consumption, it was found that certain undesirable organisms were present. To make the meat safe for consumption, it is ordered that the meat be kept at a temperature of at least 121°C for a period of at least 20 min during the preparation. Assume that a 2.5-cm.-thick slab of this meat is originally at a uniform temperature of 27°C, that it is to be heated from both sides in a constant temperature oven; and that the maximum temperature meat can withstand is 154°C. Assume furthermore that the surface coefficient of heat transfer remains constant and is 10 W/(m2 K). The following data can be assumed for the sample of meat: specific heat = 4184 J/(kg K); density = 1280 kg/m3; thermal conductivity = 0.48 W/(m K). Calculate the oven
temperature and the minimum total time of heating required to fulfill the safety regulation.
GIVEN
• A slab of meat is heated in constant temperature over
• Meat be kept at a temperature of at least 121°C for a period of at least 20 min during the preparation
• Slab thickness (2L) = 2.5 cm = 0.025 m
• Initial uniform temperature (To) = 27°C
• The maximum temperature meat can withstand is 154°C
• Specific heat (c) = 4184 J/(kg K)
• Density (?) = 1280 kg/m3
• Thermal conductivity (k) = 0.48 W/(m K)
FIND
• The minimum total time of heating required to fulfill the safety regulation
ASSUMPTIONS
• The surface heat transfer coefficient ( h c)= 10 W/(m K)
• Edge effects are negligible
• One dimensional conduction
SKETCH
