Brakes and Clutches PDF

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Mechanical EngineeringCorrelation Courses (ME 500)Brakes and ClutchesLecture: A band brake is installed on a drum rotating at a 250 rpm, and a diameter of 900 mm. the angle of contact is 1 pi radians and one end of the brake band is fastened to a fixed pin while the other end to the brake arm 150 mm...

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University of Mindanao Mechanical Engineering Correlation Courses (ME 500) Brakes and Clutches Lecture: 1.

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A band brake is installed on a drum rotating at a 250 rpm, and a diameter of 900 mm. the angle of contact is 1.5 pi radians and one end of the brake band is fastened to a fixed pin while the other end to the brake arm 150 mm from the fixed pin. The coefficient of friction is 0.25 and the straight brake arm is 1000 7. mm long and is placed perpendicular to the diameter bisecting the angle of contact. Determine the net belt pull in kN applied at the kilowatts is being absorbed. a. 4.24* b. 3.90 c. 4.0 d. 3.8 A simple band brake has a 76 cm and fitted with a steel band 2/5 cm thick 8. lined with a brake lining having a coefficient of friction of 0.25. the arc of contact is 245 deg. the drum is attached to a 60 cm hoisting drum that sustain a rope load of 820 kg. the operating force has a moment arm of 1.50 m and the band is attached 12 cm from the pivot point. Find a torque just required to support the load (clockwise) a. 2413.26 N-m* b. 3492.31 N-m 9. c. 2453.29 N-m d. 1894.82 N-m A brake shoe is pressed against the surface of a 25.4 cm diameter drum rotating at 1250 rpm with a force of 111.20 N. If the coefficient of friction between drum and cylinder is 0.21, what power is dissipated in the form of heat by the drag of the brake shoe? 10. a. 388.2 W* b. 394.9 W c. 401.6 W d. 408.8 W A cone clutch has an angle of 10 degrees and a coefficient of friction of 0.42. find the axial force required if the capacity is 7.46 KW at 500 rpm. The mean diameter of the active conical section is 11. 300mm. a. 0.40332 kN b. 0.3928 kN* c. 0.2453 kN d. 0.2384 kN An engine 40 kW at 1200 rpm, with a single plate clutch with two pairs of friction surfaces transmitting the power. Consider the coefficient of friction to be a 0.30 and mean diameter of disc to be 200 mm, determine the axial force 12. required to engine the clutch and transmit the power. a. 4.832 kN b. 5.305 kN* c. 3.693 kN d. 6.922 kN A disc clutch has a 6 pairs of containing friction surfaces. The frictional radius is 2-in and the coefficient of friction is 0.3. An axial force of 100 lb acts on the

clutch. The shaft speed is 400 rpm. How 13. much horsepower can be the clutch transmit? a. 2.28 hp* b. 3.12 hp c. 5.2 hp d. 4.51 hp A multiple disc clutch of 10 steel disc and 9 bronze disc. the effective outside 14. and inside diameter are 20.32 cm and 15.24 cm, respectively if the axial force of 450 Newton is applied and the shaft turns at 1200 rpm, find the horsepower capacity, assume a coefficient of friction of 0.27. a. 39.566 hp* b. 40.482 hp c. 37.456 hp d. 35. 659 hp An engine of a motor vehicle with a wheel diameter of 712 mm develops 50 kW at 2,000 rpm combined efficiency of the differential and transmission is 75% with an over-all speed reduction to. Determine the torque to be delivered by the clutch N-m. a. 239 N-m* b. 359 N-m c. 432 N-m d. 471 N-m A sleeve bearing has an outside diameter of 1.5 in and a length of 2 in, the wall thickness is 3/16 in. The bearing is subjected to a radial load of 450 lb. Find the bearing pressure. a. 100 psi b. 150 psi c. 200 psi* d. 250 psi Determine the machining time to drill a hole of 20 mm diameter in a workpiece 25 mm thick by a drill at a cutting speed of 30 m/min with a feed of 0.2 mm/rev. a. 17.6 s b. 14.5 s c. 19.5 s* d. 22.9 s A carbide milling cutter 250 mm in diameter is used to cut a block mild steel with a plain cutter. The block is 500 mm long. If the feed is 0.50 mm/rev and depth of cut is 1.2 mm, determine the time required to take one cut. The over travel is 16 mm. the cutting speed is 80 m/min. a. 8.45 min b. 7.45 min c. 9.45 min d. 10.45 min* Determine the time required to turn a brass component 50 mm diameter and 100 mm long at a cutting speed of 36 m/min. the feed is 0.4 and only one cut is taken. a. 2.2 min b. 3.3 min c. 1.2 min* d. 4.4 min

Prepared by: Engr. Edgar Kenneth Luna ME 500 Coordinator

A tool will cut for 4 hrs before it needs sharpening. Determine the time charged to one cycle if it takes 12 minutes to change the tool can be sharpened 10 times before it is discarded. a. 62 m/min b. 82 m/min* c. 72 m/min d. 52 m/min Calculate the power consumed during cutting of a low carbon steel bar 40 mm diameter if cutting force is 150 kg at 200 rpm. a. 0.46 hp b. 0.66 hp c. 0.75 hp d. 0.83 hp*

University of Mindanao Mechanical Engineering Correlation Courses (ME 500) Brakes and Clutches

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A 10 m3 vessel contains 5 m3 of liquid water and 5 m3 of saturated water vapor at 100kpa. Calculate the internal energy of the system using the steam tables. 5 x 105 kJ 8 x 105 kJ 1 x 106 kJ 2 x 106 kJ* 3.0 lbm of air are contained at 25 psia and 100 °F. Given that Rair = 53.35 ft-lbf / lbm-°F, what is the volume of the container? 10.7 ft3 14.7 ft3 15 ft3 24.9 ft3 * Twenty grams of oxygen (O2) are compressed at a constant temperature of 30°C to 5 % of their original volume. What work is done on the system? 824 cal 924 cal 944 cal 1124 cal * A vessel with a volume of 1 cubic meter contains liquid water and water vapor equilibrium at 600 kPa. The liquid water has a mass of 1 kg. Using the steam tables, calculate the mass of the vapor. 0.99 kg 1.57 kg 3.16 kg* 2.54 kg A cylinder and a piston arrangement contains saturated water vapor at 110 °C. The vapor is compressed in a reversible adiabatic process until the pressure is 1.6 MPa. Determine the work done by the system per kilogram of water. -637 kJ/kg -509 kJ/kg -432 kJ/kg* -330 kJ/kg Ideal Oxygen is throttled at 140degF from 10 atm to 5 atm. What is the temperature change? 0* Negative Infinity 1 Gas is enclosed in a cylinder with a weighted piston as the top boundary. The gas is heated and expands from a volume of 0.04 m3 at a constant pressure of 200 kPa. Calculate the work done by the system. 8 kJ* 10 kJ 12 kJ 14 kJ Assume the total heat of vaporization (per gram) of water can be used to supply the energy

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Prepared by: Engr. Edgar Kenneth Luna ME 500 Coordinator

needed to tear 1 g of water molecules apart from each other. How much energy is needed per molecule for this purpose? 6.74 x 10-20 J* 1.74 x 10-20 J 3.74 x 10-20 J 2.74 x 10-20 J An isobaric steam generating process starts with saturated liquid at 20 psia. The change in entropy is equal to the initial entropy. What is the change in enthalpy during the process? (Hint: Not all liquid is vaporized.) -230.4 BTU/lbm 230.4 BTU/lbm* 0 BTU/lbm 196.2 BTU.lbm A steam generator produces saturated steam at 100 psia from saturated liquid at 14.7 psia. If the heat source is a bath at 340F that produces 800 BTU/lbm, which of the following is true? The device cannot work because the pressure gradient is greater than zero. The device can work, but is inefficient. The device violates the 1st law of thermodynamics.* The device violates the 2nd law of thermodynamics. If air is at a pressure, ρ , of 3200 lbf/ft2, and at a temperature, T , of 800°R, what is the specific volume, v? (R = 53.3 ft-lbf/lbm°R, and air can modeled as an ideal gas) 9.8 ft3/lbm 11.2 ft3/lbm 13.3 ft3/lbm* 14.2 ft3/lbm A 5m3 vessel initially contains 50 kg of lquid water and saturated water vapor at total internal energy of 27,3000 kJ. Calculate the heat requirement to vaporize all of the liquid. 100,000 kJ* 2,000,000 kJ 300,000 kJ 400,000 kJ A copper can of negligible heat capacity contains 1 kg of water just above the freezing point. A similar can contains 1 kg of water just below the boiling point. Two cans are brought to into thermal contact. Find the change in entropy of the system? 100 J* 200 J 300 J 400 J The atomic weight of hydrogen is 1gram per gram-atom. What is the mass of hydrogen atom?

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1.66 x 10-24 g/atom* 6.02 x 10-10 g/atom 1.0 x 10-23 g/atom 1 g/atom In a gaseous mixture of 20 deg. C the partial pressures of the components are as follows: Hydrogen, 200 mmHg; Carbon Dioxide, 150 mmHg; Methane, 320 mmHg; Ethylene, 105 mmHg. What is the total pressure of the mixture? 755 mmHg* 255 mmHg 345 mmHg 800 mmHg Air undergoes an isentropic compression from 14.7 psia to 180.6 psia. If the initial temperature is 68 °F and the final temperature is 621.5 °F, calculate the work done by the gas. -136.2 BTU/lbm -94.8 BTU/lbm* 0 BTU/lbm 94.8 BTU/lbm Gas is enclosed in a cylinder with a weighted piston as the top boundary. The gas is heated and expands from a volume 0.04 m3 to 0.1 m3. The pressure varies such that PV = C, and the initial pressure is 200 kPa. Calculate the work done by the system. 6.8 kJ 7.33 kJ* 9.59 kJ 12.0 kJ From the steam tables, determine the average constant pressure specific heat (Cp) of steam at 10 kPa and 45.8°C. 1.79 kJ/kg.°C* 10.28 kJ/kg.°C 30.57 kJ/kg.°C 100.1 kJ/kg.°C For an ideal gas, what is the specific molar entropy change during an isothermal process in w/c the pressure changes from 200 kPa to 150 kPa? 2.00 J/moleK 2.39 J/moleK* 2.79 J/moleK 3.12 J/moleK What is the value of the work done for a closed, reversible, isometric system? Zero* Positive Negative Positive or negative If 1 lbm of steam at 14.7 psia, 63 % quality is heated isentropically, at what pressure will it reach the saturated vapor state? 56 psia 313 psia 1852 psia

University of Mindanao Mechanical Engineering Correlation Courses (ME 500) Brakes and Clutches d. 2585 psia* 22. 200g of water are heated from 5C to 100C and vaporized at a constant pressure. The heat of vaporization of water at 100C is 539.2 cal/g. The heat capacity at constant pressure, Cp is 1.0 cal/gK. Determine the total change in entropy. a. 248.2 cal/K b. 298.2 cal/K c. 348.0 cal/K* d. 398.2 cal/K 23. What is true about the polytropic exponent, n , for a perfect gas undergoing an isobaric process? a. n>0 b. n < 0 c. n → infinity d. n = 0* 24. On a hot day, the temperature rises from 50F early in the morning to 99F in the afternoon. What is the ratio of the concentration (in moles/ft3 of helium in a spherical balloon in the afternoon to the concentration of helium in the balloon in the morning? a. 0.51 b. 0.69 c. 0.91* d. 1.10 25. Cool water at 9 deg. C enters hotwater from which warm water at a temperature of 80 deg. C is drawn at an average rate of 300 g/min. How much average electric power does the heater consume in order to provide hot water at this rate? a. 4.18 kW* b. 2.35 kW c. 3.31 kW d. 5.14 kW 26. Water (specific heat cv = 4.2 kJ/kgK) is being heated by a 1500W heater. What is the rate of change in temperature of 1 kg of the water? a. 0.043 K/s b. 0.719 K/s c. 0.357 K/s* d. 1.50 K/s 27. Calculate the change in enthalpy as 1 kg of nitrogen is heated from 1000 K to 1500 K, assuming the nitrogen is an ideal gas at a constant pressure. The temperature-dependent specific heat of nitrogen is: cp = 39.06 - 512.79T-1.5 + 1072.7T-2 - 820.4T-3 cp is in kJ/Kmole-K and T is in K. a. 600 kJ b. 700 kJ* c. 800 kJ d. 900 kJ 28. Helium is compressed isothermally from 14.7 psia and 60 °F. The compression ratio is 4. Calculate the change in entropy of the gas given that RHe = 0.4961 BTU/lbm-°R.

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Prepared by: Engr. Edgar Kenneth Luna ME 500 Coordinator

-2.76 BTU/lbm-°R -0.689 BTU/lbm-°R* 0 BTU/lbm-°R 0.689 BTU/lbm-°R One kilogram of water (cv = 4.2 kJ/kg-K) is heated by 300 BTU of energy. What is the change in temperature, in K? 17.9 K 71.4 K 73.8 K 75.4 K* In an isentropic compression, p1 = 200 psia, p2 = 300 psia, V1 = 10 in3, and k= 1.4. Find V2. 3.509 in3 4.500 in3 5.000 in3 6.095 in3* 200 mL of oxygen are collected over water at 23C and a pressure of 1 atmosphere. What volume would the oxygen occupy dry at 273K and 1 atmosphere? 179.3 ml* 184.4 ml 190.0 ml 194.5 ml A gas has a density of 0.094 lb/ft3 at 100degF and 2 atm. What pressure is needed to change the density to 0.270 lb/ft3 at 250degF? 7.28 atm* 6.32 atm 3.45 atm 5.25 atm If atmospheric air 14.7 psia and 60degF at sea level, what is the pressure at 12000 ft altitude if air is incompressible. Note: @ 60degF; the density of air is 0.0763 lbm/ft3; P1 = 14.7 psia 8.342 psia* 5.34 psia 6.72 psia 9.32 psia A cold tire contains 1000 in.3 of air at 24 psia and 32degF. What pressure in the tire is needed if the temperature and volume are increased to 35degF and 1020 in.3 respectively? 23.57 psia* 32.45 psia 43.54 psia 34.57 psia Determine the specific gravity of carbon dioxide gas (molecular weight = 44) at 150degF (66degC) and 20 psia (138 kPa). 1.67* 1.45 1.87 1.30 An empty polyethylene telemetry balloon and payload have a mass of 500 lbm. The balloon is charged with helium when the atmospheric conditions are 60degF and 14.8 psia. The specific gas constant of helium is 386.3 ft-lbf/lbm-R. What

is the volume of helium is required? a. 7544 ft3 * b. 6754 ft3 c. 7455 ft3 d. 6456 ft3 37. What is the change in entropy of 2 kg water molecules when transformed at constant pressure of 1 atmosphere from water at 100degC to steam at the same temperature? a. 12.12 kJ/K* b. 10.43 kJ/K c. 9.45 kJ/K d. 10.45 kJ/K 38. In a gaseous mixture of 20 deg. C the partial pressures of the components are as follows: Hydrogen, 200 mmHg; Carbon Dioxide, 150 mmHg; Methane, 320 mmHg; Ethylene, 105 mmHg. What is the mass fraction of Hydrogen ( m(H2) = 2, m(CO2) = 44, m(meth) = 16 and m(eth) = 30 kg/mol) ? a. 0.026 * b. 0.056 c. 0.076 d. 0.016 39. Assume the total heat of vaporization (per gram) of water can be used to supply the energy needed to tear 1 g of water molecules apart from each other. What is the ratio of energy needed per molecule to kT where k = 1.38 x 10-23 J/K? a. 11.2 b. 12.5 c. 13.1 * d. 12.3 40. Steam at 1000 lbf/ft2 pressure and 300°R has a specific volume of 6.5 ft3/lbm and a specific enthalpy of 9800 lbf-ft/lbm. Find the internal energy per pound mass of steam. a. 2500 lbf-ft/lbm b. 3300 lbf-ft/lbm* c. 5400 lbf-ft/lbm d. 6900 lbf-ft/lbm 41. Calculate the entropy of steam at 60 psia with a quality of 0.6. a. 0.4274 BTU/lbm-°R b. 0.7303 BTU/lbm-°R c. 1.1577 BTU/lbm-°R* d. 1.2172 BTU/lbm-°R 42. Find the change in internal energy of 5 lbm of oxygen gas when the temperature changes from 100°F to 120°F. cv = 0.157 BTU/lbm-°R. a. 14.7 BTU b. 15.7 BTU* c. 16.8 BTU d. 147 BTU 43. Determine the change in enthalpy per lbm on nitrogen gas as its temperature changes from 500°F to 200°F. cp = 0.2483 BTU/lbm°R. a. -74.49 BTU/lbm *

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-72.66 BTU/lbm -68.47 BTU/lbm 63.78 BTU/lbm What is the resulting pressure when one pound of air at 15 psia and 200°F is heated at constant a. volume to 800°F? b. 15 psia c. 28.6 psia* d. 36.4 psia 53. 52.1 psia What horsepower is required to isothermally compress 800 ft3 of air per minute from 14.7 psia to 120 psia? 28 Hp 108 Hp* 256 Hp 13,900 Hp Calculate the work done by a system in which 1 kg mole of water completely evaporates at 100°C and 1 atmosphere pressure. 1000 kJ power. 2130 kJ a. 2490 kJ b. 3050 kJ* c. What is the equation for a work d. done by a constant temperature 54. system? W = mRTln(V2 – V1) W = mR(T2 – T1)ln V2/V1 W = mRTln V2/V1 * W = RTln V2/V1 A piston-cylinder system contains a gas which expands under a constant pressure of 1200 lbf/ft2. If work. the piston is displaced during the process, and the piston diameter is 24”, what is the work done by the gas on the piston? 1768 ft-lbf a. b. 1890 ft-lbf c. 2387 ft-lbf d. 3768 ft-lbf* 55. How does an adiabatic process compare to an isentropic process? Adiabatic: heat transfer = 0; Isentropic: heat transfer ≠ 0. Adiabatic: heat transfer ≠ 0; a. Isentropic: heat transfer = 0. b. Adiabatic: reversible; Isentropic: c. not reversible. d. Both: heat transfer = 0; Isentropic: 56. reversible.* In an adiabatic, isentropic process, p1 = 200 psia, p2 = 300 psia, and T1 = 700 °R. Find T2, using γ= 1.4. 576 °R 590 °R 680 °R 786 °R* Nitrogen is expanded isentropically. Its temperature a. changes from 620 °F to 60 °F. Find b. the pressure Ratio (p1/p2). c. 0.08 d. 12.9* 57. 23.2 3547 Nitrogen is expanded isentropically. Its temperature

Prepared by: Engr. Edgar Kenneth Luna ME 500 Coordinator

changes from 620 °F to 60 °F. The volumetric ratio is V2/V1 = 6.22 and the value of R for nitrogen is 0.0787 BTU/lbm-°R. What is the work done by the gas? -1112.7 BTU/lbm -99.22 BTU/lbm 1112.7 BTU/lbm 99.22 BTU/lbm* A device that is meant to extract power from waste process steam starts w/ steam of 75% quality at 100 psia. The exit conditions of the steam are 70% quality at 14.7 psia. Which of the following statements are true? I. The device violates the 1st law of thermodynamics. II. The device violates the 2nd law of thermodynamics. III. The device generates positive net power IV. The device generates no net I II III* IV An engineer devices a scheme for extracting some power from waste process steam. The steam enters a device at 100 psi and quality 75% and exits at 14.7 psia and 65% quality. Which of the following statements are true? I. The produces 155 BTU/lbm of II. The device violates 2nd law of thermodynamics. III. The device violates the 1st law of thermodynamics. I II III I and II * A bicycle tire has a volume of 600 cm3. It is inflated with CO2 to a pressure of 80 psi at 20C. How many grams of CO2 are contained in the tire? 3.03 g 4.83 g 5.98 g * 6.43 g When 0.5 g of a liquid is completely evaporated and collected in a 1 liter manometer, the pressure is 0.25 atmospheres and the temperature is 27C. Assuming ideal behaviour, determine the molecular weight. The gas constant is R=0.0821 atm/moleK. 2g 2.2 g 12.3 g 49.2 g* A 0.064 kg octane vapor (MW = 114) is mixed 0.91 kg of air (MW = 29.0) in the manifold is 86.1 kPa, and the temperature is 290 K. Assume octane behaves ideally,

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what is the total volume of this mixture? 0.895 cu. m. * 0.987 cu. m. 0.565 cu. m. 0.654 cu. m. Determine the sp.heat weight of air at 760 mmHg absolute and 22C? a. A.1.014 kg/m3 b. B. 1.316 kg/m3 c. C. 1.197 kg/m3 * d. D. 1.266 kg/m3 How long could a 2000 hp motor be operated on the heat energy liberated by 1 mi.3 of ocean of water when the temperature of the water is lowered by 1degC and if all these heat were converted to mechanical energy? 371.56 * 243.55 384.76 yrs 376.57 yrs Given that molar Cp of CO2 is 8.92 BTU (lb.moleR) and molar Cp of N2 is 6.95 BTU/(lbmoleR), the calculated Cp per pound of mixture containing 25% vol. CO2 and 75% vol. N2 is: 0.23 BTU/lbR * 2.23 BTU/lbR 5.21 BTU/lbR 7.44 BTU/lbR A mixture at 14.7 psia and 68F that is 30% weight CO2 (m wt=44) and 7% wt. N2 (m wt=28) has a partial pressure of CO2 in psia that is nearest to: 2.14 3.15 * 6.83 7.86 Normal boiling point of liquid oxygen is 90K. What is its temp in R? -330R -183R 162R* 168R Shaft work of -15 BTU/lb and heat transfer of -10 BTU/lb change enthalpy of a system by: -25 BTU/lb -15 BTU/lb -10 BTU/lb +5 BTU/lb* A non-flow (closed) closed system contains 1lb of an ideal gas (Cp = 0.24, Cv = 0.17). The gas temperature is increased by 10F while 5 BTU of work are done by the...