A succession of 2-m long water waves on a lake goes by a piece of floating cork that bobs up and down one complete cycle each second. What is the speed of the wave?
A) 0.25 m/s
B) 0.50 m/s
C) 1.0 m/s
D) 2 m/s
E) 4 m/s
Answer: D
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A change in a physical quantity w having initial value wi and final value wf is given by which of the following?
a. wi ? wf b. wf ? wi c. (wf + wi)/2 d. none of the above
This diagram shows two energy levels in an atom. The lower level is "full" because it already has an electron with spin up and another with spin down. Therefore, a third electron must go into the higher energy level. What law or principle explains why?
A) the exclusion principle B) the uncertainty principle C) the law of conservation of angular momentum D) the law of conservation of energy
What elements do the symbols H, O, C, and N stand for?
a. hydrogen, ozone, carbon, nitrogen b. hydrogen, oxygen, chlorine, nitrogen c. hydrogen, oxygen, carbon, natrium d. hydrogen, oxygen, carbon, nitrogen e. none of the above
Hot water is used to heat air in a double pipe heat exchanger as shown in the following sketch. If the heat transfer coefficients on the water side and on the air side are 550 W/(m2K) and 55 W/(m2 K), respectively, calculate the overall heat transfer coefficient based on the outer diameter. The heat exchanger pipe is 5 cm, schedule 40 steel (k = 54 W/m K), with water inside but assume that a fouling factor of 0.173 (m2 K ) /kW based on the tube outside diameter has developed over time.
GIVEN • A double pipe heat exchanger with water in inner tube and air in the annulus • Heat transfer coefficients ? Water side h i= 550 W/(m2 K) ? Air side h o= 55 W/(m2 K) • Inner pipe: 2 in., schedule 40, made of steel • Pipe thermal conductivity (k) = 54 W/(m K) • Fouling factor (Rd) = 0.173 (m2 K )/kW= 1.73*10-4 (m2 K )/kW, based on the tube outside area FIND • The overall heat transfer coefficient based on the outer diameter (Uo) ASSUMPTIONS • Uniform heat transfer coefficients • The given fouling factor is based on the outer tube diameter (Do)