Which of the following molecules contains a phenol?
A) a
B) b
C) c
D) b and c
E) all of them
Answer: D
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Imagine a downhill race between four objects each of mass M. One object such as a skier (P) is best modeled as a particle (shown as a small flat object) translating down the hill. The other objects are modeled as a solid cylinder (C), hoop (H) and a solid sphere (S) each of radius R rolling down the hill without slipping. All four objects start from rest a t a height h. Assuming mechanical energy losses due to friction may be ignored, determine the order in which the objects cross the finish line. Use their letter designation: P, C, H and S and arrange them from first to last to arrive at the finish line.
Given that the charge on an up quark is +2/3 and the charge on a down quark is ?1/3, which combination represents a neutron?
A. uud B. udd C. uuu D. ddd
A large high-power transformer is installed and operated in an electric-power distribution station. To maintain transform efficiency and prevent its failure (burnout), the transformer oil is cooled via a water-cooled, coiled tube heat exchanger and circulated through the transformer winding module. For one such application, transformer oil, with a flow rate of 0.3 kg/s, is to be cooled to 30°C while flowing through the coiled thin walled metallic tubing. The tube has an inner diameter of 5.0 cm, and its surface is maintained uniformly at a temperature of 20°C. If the oil enters the heat exchanger tube at a temperature of 50°C, and if the coil effects can be ignored and tube modeled as a straight circular pipe, what is the tube length required for this heat exchanger? What is the
expected pressure drop across the tube length? Also, if the tube surface temperature increases to 25°C, determine the outlet temperature of transformer oil for the calculated pipe length.
GIVEN
• Transformer oil cooled via water-cooled, coiled tube heat exchanger.
• Oil flow rate, m = 0.3 kg/s.
• Oil inlet temperature, Tb,in = 50°C.
• Oil outlet temperature Tb,out=300C
• Inner or inside diameter of pipe in which oil flows, D = 5 cm = 0.05 m.
• Temperature of pipe surfaceTs = 20°C.
FIND
• Length of tube required for heat exchanger
• Oulet temperature is surface temperature reaches to 250C for given length.
ASSUMPTIONS
• The temperature of wall is constant and uniform across the length of pipe.
• The thermal resistance of the pipe is negligible, and hence the inside surface temperature of the pipe is Tw = Ts, this represents a uniform pipe surface temperature condition.
SKETCH
You are heating two chunks of metal of the same size and shape. One is made of lead and is heated to 400 K. The other is made of iron and is also heated to 400 K. Which of the following statements apply to the thermal radiation the two chunks emit?
A) The two spectra peak at the same wavelength. B) The spectra cannot be compared because they come from different materials. C) The lead spectrum peak is at a shorter wavelength than the iron spectrum peak. D) The lead spectrum peak is at a longer wavelength than the iron spectrum peak.