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quiz 2 - Quiz 2 ME 300 Fall 2008 Your NAME(pl write in bold...

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Unformatted text preview: Quiz # 2 ME 300 Fall 2008 Your NAME (pl. write in bold): V A N \4. A Answer all questions. Do not circle two answers; they will be invalidated. There is no partial credit. Please DO NOT consult text book, class notes, HW solutions, or your neighbor students. Strict penalties for violations will be imposed, as per university rules. 1. A thermodynamic process occurs according to the relation p V 2 = constant. The initial state of the gas is p = 2 bars, V = 2 m3. In the final state p = 4 bars. The final volume is given by 2. 2.. )3 3 Pfi/l : P7“ V9" 7. a m b) 4m3 V2?“ t» :3... Vi} =2 9:2” )2) .414m3 ‘92 “3 d) 2.818m3 Va -: 3.. -= \le =~ Mm” 2. A big rock weighing 500 kg is dropped in free fall (initial velocity = 0) from a height of 100 m. The gravitational acceleration g = 9.81 m/sz. Neglecting air resistance, the velocity when it hits the ground is approximately equal to: a) 98.1m/s AVE .1. APE. 1: O 19.62m/s AVE. = _ APE :; _m (%)<O_\OO> @ 44.3m/s 7, 2 , \ 000(3) .L. —V r. . (m) la) 6'5 ‘ 3132 ”V5 9' MM; do) Va :_ imm) £23009)?! /2 : 44 .3 m/: 3. Natural gas is compressed in a piston—cylinder assembly by the relation pV = const. The initial volume is 0.2 ft3, and the final volume is 0.1 ft3. The initial pressure is 15 Ibf/inz. The work required to compress the gas is: a) Zero V )Infinite N 3' ‘5' Vl 9m ’5'? (N ‘> (a) 299 6ft|bf :2 US) rum)” 9.» 39:3 )2 08 ft. lbf ‘9 4. An electric battery is charged by passing a current of 4 amps across a voltage of 15 V. if the battery is charged for a period of 12 hrs., the total electricity consumed is: ... 05% W. fcwu '; E'- l" a) 72 kWh b) 720 kWh Ema ._._ (53; ,4 V3- @o.72 kWh loco \n d) 0.6 kWh “‘ ‘3 "l ’1 WA 5. Heat transfer occurs across the surroundings of a thermodynamic system, while the system performs work simultaneously. The heat transferred to the system is measured to be 35 kJ, and the work done by the system is 29 kJ. The net change in systems energy is: AE: G—W a) 60k] 35-. Qq : G k:- b) —60 kJ 3'- 6 kl d) 35 kJ. e) None of the above 6. A certain gas in a piston—cylinder assembly expands from an initial volume of 0.2 ft3 to 0.4 ft3. The pressure is maintained constant at 28 lbf/inZ. What is the work done by the system in Btu? (1 Btu = 778 ft. lbf) p; eonskam’c a. my” in?” .. n. ,. ...o.2 *L'fi‘ V‘l -— l? (Vi; \fl) - (133(0 L‘ >778 \. oaks 3*“ ...
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