Contra Academicos - Cristian David Ávila Valbuena

310. Water (specific heat cv= 4.2 kJ/ kg ∙ K ) is being heated by a 1500 W h eater.

What is the rate of change in temperature of 1kg of the water?

 A. 0.043 K/s

 B. 0.179 K/s

 C. 0.357 K/s

 D. 1.50 K/s Formula: Q = mcv ( T)∆

311. A system weighing 2kN. Determine the force that accelerate if to 12 m/s^2.

a. vertically upward when g = 9.7 m/s^2

 A. 4474.23 N

 B.5484.23 N

 C.4495.23 N

 D.5488.23 N Formula: F = m/k (a +g)

312. Refer to problem # 11. Determine the force that accelerates if to 12 m/s^2.

horizontally along frictionless plane.

 A. 2474.23 N

 B. 2574.23 N

 C. 3474.23 N

 D. 2374.23 N Formula :

M = wk / g F = ma /k

313. A problem Drum ( 3 ft. diameter ; 6 ft. height ) is field with a fluid whose density is 50 lb/ft^3. Determine the total volume of the fluid.

 A. 42.41 ft^3

 B.44.35 ft^3

 C.45.63 ft^3

 D.41.23 ft^3

Formula: Vf = (pi d^2 h) / 4

314. What is the resulting pressure when one pound of air at 15 psia and 200 ˚F is heated at constant volume to 800 ˚F?

 A.15 psia

 B. 28.6 psia

 C. 36.4 psia.

 D. 52.1 psia Formula :

T1/p1 = T2/p2 p2= p1T2 / T1

315. What horse power is required to isothermally compress 800 ft^3 of Air per minute from 14.7 psia to 120 psia?

 A. 28 hp

 B.108 hp

 C.256 hp

 D.13900 hp

Formula: W= p1V1 ln (p1/p2) Power = dW / dt

316. What is the equation for the work done by a constant temperature system?

 A. W = mRTln(V2-V1)

 B. W = mR( T2-T1 ) ln( V2/V1)

 C. W = mRTln (V2/V1)

 D. W = RT ln (V2/V1) Formula : W=∫ pdV lim1,2

∫ = mRT / V

317. Twenty grams of oxygen gas are compressed at a constant temperature of 30 ˚C to 5%of their original volume.

What work is done on the system.

 A.824 cal

 B.924 cal

 C.944 cal

 D.1124 cal Formula:

W = -mRTln (V2/V1)

Where R = (1.98 cal/gmole·K) (32 g/gmole)

318. Helium ( R= 0.4698 BTU/lbm-˚R ) is compressed isothermally from 14.7 psia

and 68 ˚F. The compression ratio is 1:4.

Calculate the work done by the gas.

 A. –1454 BTU/lbm

 B. -364 BTU/lbm

 C.-187BTU/lbm

 D.46.7 BTU/lbm Formula: W = RT ln (V2/V1)

319. Gas is enclosed in a cylinder with a weighted piston as the stop boundary.

The gas is heated and expands from a volume of 0.04 m^3 to 0.10 m^3 at a constant pressure of 200kPa.Calculate the work done by the system.

 A. 8 kJ

 B. 10 kJ

 C.12 kJ

 D.14 kJ

Formula: W = p(V2-V1)

320. refer to problem no.13. Determine the specific volume.

 A. 0.02 ft^3/lbm

 B. 0.05 ft^3/lbm

 C. 1.0 ft^3/lbm

 D. 1.2 ft^3/lbm Formula :

Vf = ( pi d^2 h) / 4 Pf = mf / vf

Specific volume= Vf /mf

321. What is the weight of a66-kgm man at standard condition?

(Formula: Fg= mg / k)

 a. 66 kgf

 b. 66 kgm

 c. 66 lbm

 d. 66 gf

322. What is the specific weight of water at standard condition?

(Formula: γ = ρg / k)

 a. 1000 kgm/m³

 b. 9.8066 m/s²

 c. 1000 kgf/m³

 d. None of the above 323. 746 °R = ______ °F

 a. 254

 b. 345

 c. 286

 d. None of the above

324. A 30-m vertical column of fluid (density 1878 kg/m³) is located where g=

9.65 mps². Find the pressure at the base of the column.

(Formula: pg= gρhg/k )

 a. 543680 N/m²

 b. 543.68 kPa (gauge)

 c. Both a & b

 d. None of the above

325. Ten cu ft. of air at 300 psia 400°F is cooled to 140°F at constant volume.

What is the final pressure?

(formula: p2 = p1T2/T1)

 a. 0

 b. 209 psia

 c. - 420 psia

 d. None of the above 326. 876 °R = _____ °F

 a. 335

 b. 416

 c. 400

 d. None of the above

327. There are 1.36 kg of gas, for which R = 377 J/kg.k and k = 1.25, that

undergo a nonflow constant volume process from p1 = 551.6 kPa and t1 = 60°C to p2 = 1655 kPa. During the process the gas is internally stirred and there are also added 105.5 kJ of heat.

Determine t2.

(Formula: T2= T1p2/ p1)

 a. 999 K

 b. 888 K

 c. 456 K

 d. One of the above 328. 5 atm = ____mmHg

 a. 8300

 b. 3800

 c. 3080

 d. None of the above 329. A certain gas, with cp =

0.529Btu/lb.°R and R = 96.2 ft.lb/lb.°R, expands from 5 cu ft and 80°F to 15 cu ft while the pressure remains constant at 15.5 psia. Compute for T2.

(Formula: T2= T1V2/V1)

 a. 460°R

 b. 270°R

 c. 1620 °R

 d. None of the above

330. In the above problem, compute for the mass.

(Formula: m = p1V1 / RT1)

 a. 0.2148 lb

 b. 0.2134 lb

 c. 0.1248 lb

 d. None of the above 331. 710°R= ______ °C

 a. 214

 b. 121

 c. 213

 d. None of the above 332. 212 °F = _____ °C

 a. 200

 b. 150

 c. 100

 d. None of the above

333. Let a closed system execute a state change for which the heat is Q = 100 J and work is W = -25 J. Find E.∆

(Formula: E = Q- W)∆

 a. 125 J

 b. 123 J

 c. 126 J

 d. None of the above

334. A pressure gage registers 50 psig in a region where the barometer is 14.25 psia. Find absolute pressure in psia, Pa.

(Formula; p = patm+ pg)

 a. 433 kPa

 b. 443 kPa

 c. 343 kPa

 d. None of the above

335. A mass of 5kg is 100m above a given datum where local g = 9.75 m/s². Find the gravitational force in newtons.

(Formula: Fg= mg/k )

 a. 48.75 N

 b. 50 N

 c. 45 N

 d. None of the above

336. In the above problem, find the potential energy of the mass with respect to datum.

(Formula: P = mgz/k )

 a. 4875 j

 b. 0.51 j

 c. 0.46 j

 d. None of the above

337. The combined mass of car and passengers travelling at 72 km/hr is 1500 kg. Find the kinetic energy of this combined mass.

(Formula: K =mv²/ 2k )

 a. 300 kJ

 b. 200 kJ

 c. 500 kJ

 d. None of the above 338. 14.696 psia = _____ mmHg

 a. 760

 b. 1

 c. 350

 d. None of the above 339. 212 °C = _____ K

 a. 485

 b. 435

 c. 498

 d. None of the above 340. 212 °F = _____R

 a. 567

 b. 672

 c. 700

 d. None of the above

341. An automobile tire has a gauge pressure of 200 kpa at 0°C assuming no air leaks and no change of volume of the tire, what is the gauge pressure at 35ºC.

 a. 298.645

 b. 398.109

 c. 291.167

 d. 281.333 Pg = Pabs - Patm

342. An ideal gas at 45psig and 80ºF is heated in the close container to 130ºF.

What is the final pressure?

 a. 65.10 psi

 b. 65.11 psi

 c. 65.23 psi

 d. 61.16 psi

P1V1/T1= P2V2/T2;V = Constant

343. A wall of the firebrick has an inside temperature of 313ºF and an outside temperature of 73ºF. What is the

difference in the surface temperature in Rankin?

 a. 70

 b. 68

 c. 72

 d. 94 ºR = ºF + 460

344. What is the force required to accelerate amass of 30kg at a rate of 15m/s².

 a. 460 N

 b. 380 N

 c. 560 N

 d. 450 N F = ma

345. How much does an object having the mass of 100kg weight in newton.

 a. 981 N

 b. 991 N

 c. 981.6 N

 d. 980.1N F = ma

346. The volume of the gas held at constant pressure increases 4 cm² at 0°C to 5cm². What is the final pressure?

 a. 68.65ºC

 b. 68.25ºC

 c. 70.01°C

 d. 79.1ºC t2= T2–T1

347. A certain gas with cp = 0.529Btu/lb°R and R = 96.2ft/lbºR expands from 5 ft and 80ºF to 15 ft while the pressure remains constant at 15.5 psia.

 a. T2=1.620ºR, ∫H = 122.83 Btu

 b. T2 = 2°R, ∫H = 122.83 Btu

 c. T2 = 2.620ºR, ∫H = 122.83 Btu

 d. T2 = 1°R, ∫H = 122.83 Btu T2= V2(t2)/V1 and ∫H = mcp (T2-T1) 348. A vacuum is connected to a tank reads 3kpa at a location w/ the

barametric pressure reading is 75mmhg.

Determined the P absolute in the tank

 a. 70.658 kpa

 b. 68 kpa

 c. 58.78 kap

 d. None of the above Pabs = Patm – Pvacuum 349. Calculate:

a. Mass flow rate in lb/hr.

b. The velocity at section 2 in fps

 a. 800,000lb/hr;625ft/s

 b. 900,000lb/hr;625 ft/s

 c. 888,000lb/hr;269 ft/s

 d. 700,000lb/hr;269 ft/s m = A1V!/V1

350. A 600kg hammer of a pile driver is lilted 2m the pilling head. What is the change of potential energy? If the hammer is realest. What will be its velocity and the instant if it sticks the pilling?

 a. 10,772 N-m and 5.26m/s

 b. 13,200 N-m and 5.26m/s

 c. 11,772 N-m and 6.26m/s

 d. 11,77 2N-m and5.26m/s

∫PE = mgo(∫Z)/gc

In document Cristian David Ávila Valbuena (página 43-47)