The source of energy in the Sun is
A. uranium chain reaction
B. radioactivity of tritium
C. fusion of hydrogen
D. radioactivity of potassium-40
Answer: C. fusion of hydrogen
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The Moon's near side always faces Earth due to
A) the Sun's gravity. B) the solar wind. C) Earth's magnetic field. D) conservation of angular momentum in the solar nebula. E) Earth's tidal force.
In a biomedical processing plant, a newly developed liquid drug or medication that leaves a mixing chamber at 20°C needs to be heated to 70°C in a thermal curing process. This is achieved by heating the liquid media at the rate of 10 kg/h in a thin metallic circular pipe with a 10 mm inner diameter that is electrically heated by wrapping it in resistance wire and insulation. If the tube surface is heated with a constant heat flux of 5,100 W/m2, calculate the length of tubing needed for this heat exchange device and the inner surface temperature of the pipe at its exit. Assume fully developed convection, and verify this assumption after calculating the length. The physical properties of the fluid media are considered as follows: Cp= 4.0 kJ/(kg K), k= 0.5 W/(m K), ?= 0.002 Ns/m2, and
?=1000 kg/m3 GIVEN • Diameter of copper tube (Di)= 10 mm = 0.01 m • Cooling water inlet temperature (Tin)= 200C • Cooling water flow rate ( m• )=10 kg/hr = 2.78*10-3 kg/s • Cooling water outlet temperature (Tout)= 700C • Surface heat flux(q’’) = 5100 W/m2 FIND (a) Length of tubing needed for this heat exchange device. (b) Inner surface temperature of pipe at exit. PROPERTIES AND CONSTANTS Given, for the fluid Density (?) = 1000 kg/m3 Specific heat (cp) = 4000 J/(kg K) Thermal conductivity (k) = 0.5 W/(m K) Absolute viscosity (?) = 0.002 (Ns)/m2
In the equation ac= v2/r for centripetal acceleration, the r stands for
a. diameter. b. distance. c. radius. d. rate.
A beam of light, traveling in air, strikes a plate of transparent material at an angle of incidence of 56.0°. It is observed that the reflected and refracted beams form an angle of 90.0°. What is the index of refraction of this material?
A) 1.40 B) 1.44 C) 1.43 D) 1.48