As a car drives with its tires rolling freely without any slippage, the type of friction acting between the tires and the road is
A) static friction.
B) kinetic friction.
C) a combination of static and kinetic friction.
D) neither static nor kinetic friction, but some other type of friction.
E) It is impossible to tell what type of friction acts in this situation.
A
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List these electromagnetic radiations from short to long wavelengths.
A. radio waves, ultraviolet, visible light, infrared, X-rays, gamma rays B. gamma rays, X-rays, ultraviolet, visible light, infrared, radio waves C. gamma rays, X-rays, infrared, visible light, ultraviolet, radio waves D. radio waves, infrared, visible light, ultraviolet, X-rays, gamma rays
Which of the following is true of the Sun?
A) It is a nonluminous body. B) It generates energy by nuclear fission reactions. C) It is about 100 times larger in diameter than Earth. D) It shines by reflecting light from Venus.
Which of the following statements best describes Kepler's 3rd law of planetary motion?
a. The smaller the diameter of a planet, the faster its rotational period is. b. The orbital period of a planet is directly proportional to the diameter of the planet. c. The smaller the orbit, the longer its orbital period is. d. The larger the orbit, the longer its orbital period is.
For safety reasons, a heat exchanger performs as shown in (a) of accompanying figure. An engineer suggests that it would be wise to double the heat transfer area so as to double the heat transfer rate. The suggestion is made to add a second, identical exchanger as shown in (b). Evaluate this suggestion, that is, show whether or not the heat transfer rate would double.
GIVEN
Case 1
Heat exchanger as shown above.
• Overall heat transfer coefficient times the transfer area (UA) = 40,000 kJ/(hr K)
• Heat capacity rates
? Ch = 80,000 kJ/(h K)
? Cc = 40,000 kJ/(h K)
• Entering temperatures
? Tb,in = 400 K
? Tc,in = 300 K Case 2 Two of the same heat exchanges as shown above in Figure B. FIND
• Does the heat transfer rate double?
ASSUMPTIONS
• Heat exchangers are simple counterflow geometry