PHYS2B_Midterm_SU16 Key - THERMODYNAMICS and FLUIDS EXAM...

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Unformatted text preview: THERMODYNAMICS and FLUIDS EXAM Name K C j Signature TRUEIFALSE. Write 'T' if the statement is true and 'F if the statement is false. (2 points each) 1) If two different gases are at the same temperature, the average translational kinetic energy per 1) [ molecule must be the same for both of them. 2) A heat engine that is 40% efficient and has a heat input of 200] per cycle at the hot reservoir will 2) waste 80 I of heat each cycle. 3) A refrigerator increases the entropy of its hot reservoir at the same time as it decreases the entropy 3) l of its cold reservoir. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. (2 pts. ea.) 4) Which contains more moles of material: 80 grams of helium (4He) or 400 grams of argon (40Ar)? 4) [of A) the helium _ B) the argon C) Both contain the same number of moles. 5) An ideal gas inside box A of volume V has a temperature T and contains N molecules. An ideal gas 5) C inside box B of volume V/2 has a temperature T/2, and also contains N molecules. In which box is the pressure the highest? A) Box B B) Box A C) The pressure is the same in both boxes. 6) An air bubble is formed at the bottom of a lake, and begins rising toward the surface. The air is 6) C hotter than the water. If the temperature of the air remains constant as the bubble rises, the volume of the bubble will A) remain constant. B) decrease. C) increase- 7) The oxygen molecules and the nitrogen molecules at any one place in our atmosphere are at the 7) A same temperature. How do the root—mean—square speeds of the two molecules compare (147N, 1630)? A) N2 > 02 B) same C) 02 > N2 8) A wooden block contains some nails so that its density is exactly equal to that of water. If it is 8) C placed in a tank of water and released from rest when it is completely submerged, it will A) sink to the bottom. B) rise to the surface. C) remain where it is released. 9) In the figure, fluid fills the container shown here. At which of the indicated points is the pressure greatest? A) A B) C C) B D) D E) The pressure is the same at each of the labeled points. 10) The Bernoulli effect is described by the equation P1 + mpvzi + Pglu = P2 + mpv 3 + pghz The origin of this relation is that it is a statement of A) N ewton's Third Law, i.e., equal action and reaction. B) the conservation of linear momentum. C) the conservation of energy for a moving fluid. D) the continuity principle for fluids. E) F = ma as applied to a fluid. 11) A cylinder fitted with a movable piston contains ideal gas at 270°C, pressure 0.500 x 105 Pa, and volume 1.25 m3. What will be the final temperature if the gas is compressed to 0.800 m3 and the pressure rises to 0.820 x 105 Pa? (15 points) . T; = 2.10% = 305 K Pt. 2. 0.500 34/0 S‘Pa P[ V(' ___ P4 V‘F Vi: [2,5an3 '7} TF :0 300m 7}: (3“ MT} (3‘)“) 0 $20 N0 54F T_w_s,zgggr31flm =7. 4‘ " (.o 500 2&10‘Pa)('15""‘3 T :. 314.61 K 2 arm °c or 2 g; 3(5'K :: LIZOC (29s,) (2m) 9)E 10) C (300 K) (3‘9“) 12) A 771.0 kg copper bar is put into a smelter for melting. The initial temperature of the copper is 300.0 K. How much heat must the smelter produce to completely melt the copper bar? (The specific 5 mg l Jr.“- heat for copper is 386 J/kg-K, the heat of fusion for copper is 205 kI/kg, and its melting point is C 0:91 p) 1357K.)(15 points) ( 3911-) ,. __ _ _. 300.0K QM}- m c AT _ (Htoqysgfiflzm K ) “P ”LIZ? :- 317,600,000: (Energy +0 haul-«up b4:— ( +5) (“Z—(7+5) +23 {+5 Mel-l: Pub P079?” Ca 3P ‘ PP‘F ._ bar QHM 7- MLF = (??I.OI¢5XZOOZOOOJA<9 :. 155; among; _ «H: {V1 '- ?‘?l-Olfi? 7“” (IE—“he fay (14¢ch +0 Meli' bar) T;- = 300.0 K bar (29”.) (min) QT : QM.“ 7‘ C? "-2 BIS; boo,oooy+ IS}; 0515:0003 :2 LI?3J(,55,000J :1: 7?7,000JOOOJ g: at}? was}: fir HRH/03$ 5}: Qatar/”J C7— 9“) 13) A hollow steel ball of diameter 3.00 m barely floats in water (i.e. top of the ball is at the surface of the water). What is the wall thickness of the ball? (QFe = 7.87 g/cm3 ;Vsphere = (4/3)11:r3) (15 points) M431" L-eu—«el fi :11?) (Ar-ain't M-QJ45( Principle) -- J... bauy b‘u-t - F‘m-I 1 Wmhrdwaud (30“) W a: mm mm“? 7 hell dfipl. ’Hajcrk 1: 1:?- __ h ,5 Q‘Fc\/SL¢‘N —-. Qua Vial-er bfu aflac'd Vskw: Qwvw -_— ("°°37§-E)%fi("50"‘)3 9F: (mam 3 ”S ‘5 3 3 VSl’Le\\ : 1%“ Roam" ’2’” Ram“: %fl( $6” fig 5 '7. l.‘}‘lém 33-7! (I-a'0ml3— 51:??? 2 mm? NO» 3 , mqfiygrfi : K. (%TT) 17.3Hm3:{$(_3(%n) 3 (.H'Efin: i3; (310“) : 1,?qcm3 (3915-) T‘U‘c {this} :- po- PL 2 LSD; [-7.39% '3 0.06é M2: G.écmt?cm @913.) ...
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