A sample of blood is placed into a centrifuge of radius 15.0 cm. The mass of a red corpuscle is 3.0 × 10^-16 kg, and the centripetal force required to make it settle out of the plasma is 4.0 × 10^-11 N. At how many revolutions per second should the centrifuge be operated?
150 rev/s (9 000 rpm)
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Relative to a fossil-fuel plant, a nuclear power plant produces
A) more electricity. B) less heat and smoke. C) less pollution. D) all of the above E) none of the above
A 0.6-cm-diameter mild steel rod at 38°C is suddenly immersed in a liquid at 93°C with ch = 110 W/(m2 K). Determine the time required for the rod to warm to 88°C.
GIVEN
• A mild steel rod is suddenly immersed in a liquid
• Rod diameter (D) = 0.6 cm = 0.006 m
• Initial temperature of the rod (To) = 38°C
• Liquid temperature (T?) = 93°C
• Heat transfer coefficient ( ch ) = 113.5 W/(m2 K)
FIND
• The time required for the rod to warm to 88°C
ASSUMPTIONS
• The rod is 1% carbon steel
• Constant thermal conductivity
• End effects are negligible
• The rod is very long compared to its diameter
• There is radial conduction only in the rod
SKETCH
PROPERTIES AND CONSTANTS
For 1% carbon steel at 20°C:
Thermal conductivity (k) = 43 W/(m K) Specific heat (c) = 473 J/(kg K) Density (?) = 7801 kg/m3 Thermal diffusivity (?) = 1.172 × 10–5 m2/s. [? = k/?c].
Which of the following is not one of the most common elements in living things?
a. oxygen b. carbon c. calcium d. iron e. nitrogen
All Type II supernovae produce neutron stars when they collapse
Indicate whether the statement is true or false