ME 201 PSU Multiple Choice Questions

60 kJ of energy is available in (i) a hot copper block at 100 deg C; (ii) a very hot copper block at 400 deg C; (iii) a shaft spinning. Rank these three forms of energy in the order of highest quality to lowest quality. (i), then (ii), then (iii) (iii), then (ii), then (i) (i) and (ii) , then (iii) (iii), then (i) and (ii) They are all of equal quality because all are 60 kJ

(iii), then (ii), then (i)

A car moving on a highway and we will analyze it as a fixed mass control volume (cV). At an instant, in one second, 175 kJ of Mechanical energy leaves the cV will 200 kJ of energy leaves via hot engine exhaust. Based on out sign convention, w = ____, Q= ___, deltaE = ____ +175, +200, -25 -175, -200, +25 -175, -200, +375 +175, -200, -375

+175, -200, -375

By our convention in class, work entering a system is __ and heat entering a system is __ +,+ -,+ -,- +,-

-,+

In an isobaric process, volume of a system was changed from 10 m^3 to 2 m^3 at 200 kPa. The work done, W, in this process based on the sign convention in the class is -1600 kJ 1600 kJ 25 kJ -25 kJ

-1600 kJ

The ideal efficiency of an engine operating between temperatures of 30 deg C and 60 deg C is 20 .05 .95 .65

.65

Consider a tank being filled with water at 5 gal/min. However, a person is using 4 gal/ min and there is a leak of 0.1 gal/min. What are the values for Xgen and rate of water accumulation in gal/ min? 5 and 1 5 and 0.1 0 and 0.10 and 0.9 0 and 0.9

0 and 0.9

In an isochoric process, the pressure in a system changes from 10 kPa to 20 kPa at V = 5 m^3. Calculate the work done in this process according to the sign convention in the class. -50 kJ 50 J 0 kJ 59 kJ

0 kJ

Work done in an isochoric process with V=1 m^3 and pressure changing linearly 1 kPa to 11 kPa is: 10kW 10MW 10kJ 10MJ 0.0

0.0

An object with a mass 4 kg is moving at a speed 10 m/s, Its specific KE is . . 200 kJ/kg 100 kJ/kg 50 kJ/kg 0.1 kJ/kg 0.05 kJ/kg = (1/2)V^2 = (1/2)10^2 = 50 / 1000 kJ/kg

0.05 kJ/kg = (1/2)V^2 = (1/2)10^2 = 50 / 1000 kJ/kg

I have a cup of coffee. It takes 1.0 kJ of heat energy to increase the coffee temperature through each degree on deg C scale. This also can be expressed as "the heat capacity of the coffee in this cup is 1.0 kJ/ deg C". Which of the following is correct heat capacity of the coffee? Given: 1kcal = 4.2 kJ 0.238 kcal/ deg F 0.238/ (-32 x 9/5) kcal/ deg F 0.238 x (5/9) kcal/ deg F 0.238 x (9/5) kcal/ deg F 1.0 kcal/ K

0.238 x (5/9) kcal/ deg F

A 2 kg iron block is heated from 20 deg C to 120 deg C in 1 minute 4 seconds. If the specific heat of iron is 0.45 kJ/ kgK, what is the average rate of heating? 0.9 kW = (m*C*deltaT)/(delta t) = (2*0.45*100)/100 = 0.9kW 0.9 MW 9MW 0.9kJ 9MJ

0.9 kW = (m*C*deltaT)/(delta t) = (2*0.45*100)/100 = 0.9kW

The quality x, at state 3 is ________. And at 5, is ____ respectively. x=0 and x> 1.0 x=1 and undefined 0<x<1 and undefined Undefined and undefined x=10 and undefined

0<x<1 and undefined

Fluid is described by _________ 1) molecules are free to move around, but there is a free surface, and very few escape or enter that free surface 2) molecules are free to move around the entire volume of the system 3) molecules can vibrate, but the average position of the molecules relative to each other remains fixed 1 2 3 1 or 2 1, 2, and 3

1 or 2

When you put your palm outside of a car going at a speed V, you felt some pressure pushing your hand back. Now you put your palm outside again and this time the pressure is double that of the previous pressure. Your car speed is approximately: V 1.4V 2V 4V .5V

1.4V

Pressure of "7.60 m of Mercury" in kPa is equal to _______. (Assume density of mercury = 1000kg/m3, g = 9.8m/s2) 10 kPa 10 Pa 1000 kPa 10000 kPa almost 1 atm

1000 kPa

What is RO2 / RCO2? 11/8 = (Runiv / Mw O2)( Mw CO2 / Runiv) 1 8/11 Need more information

11/8 = (Runiv / Mw O2)( Mw CO2 / Runiv)

In order to define a state completely we need ___ independent and ___ properties. 3, Extensive 3, Intensive 2, Intensive Depends

2, Intensive

The state of a simple compressible closed system can be completely defined with _____ independent _____ properties 2, extensive 1, extensive 3, extensive 2, intensive

2, intensive

If the energy emitted by a body increases by a factor of 16, the absolute temperature of the surface must have increased by a factor of (assuming that the other parameters remained the same): 2.0 4.0 8.0 16.0 64.0

2.0

Volume flow rate of a gas into a compressor is 10 m^3/s. Density of the gas is 2 kg/m^3. What is the mass flow rate [kg/s] through the compressor? 10 kg/s 20 kg/s 5 kg/s .2 kg/s

20 kg/s

A pot holding 1kg of pure water has just started to boil at constant atmospheric pressure. How much internal energy must be added to the water so that all the water becomes vapor? 2506 kJ 418.95 kJ Cannot be determined without more information 2087 kJ

2087 kJ

The sun delivers roughly 1kW/m^2 of power to the Earth's surface. A parabolic mirror w/ a 1m^2 area is used to focus this energy onto a beaker containing 1kg of water. Est the time taken by the mirror to raise the T of water from 10C to 60C, assuming the specific heat capacity of water to be 4.2 and ignoring energy losses to the surroundings 4.2s 4200s 210s 0.210s

210s

How much work is done if 0.240m^3 of argon gas is reversibly doubled in volume against 100kPa pressure? 240J 2.4kJ 24kJ 240kJ

24kJ

A mixing chamber has two inlets and one outlet. It mixes water at different temperatures. Inlet #1, m1 = 10 kg/s, h1 = 3500 kJ/kg, inlet #2, m2 = 20 kg/s, h2 = 3200 kJ/kg, what is the outlet water enthalpy? 3500 kJ/kg 3300 kJ/kg 3200 kJ/kg 3400 kJ/kg

3300 kJ/kg

A compressor requires 40 kW power: its N = 80%. Improved design. Now it is N = 90%. The power requirement under same conditions for the improved design will be 40 kW 50 kW 32 kW 36 kW

36 kW

Two rigid tanks are connected by a channel. At first, tank A contains 30kg water with TA=300K. Tank B contains 50kg of water with TB=400K. Water in the two tanks is allowed to mix adiabatically (no heat loss or gain to the surroundings). Assuming that the specific heat of water is constant, the equilibrium temperature of the mixture is = ? 332.5 K 352.5 K 362.5 K 462.5 K

362.5 K

The COP of an engine which receives 100kW from high temperature reservoir and rejects 60 kW to low temperature reservoir is 100% 60% 40% 20%

40%

3. A 15 Ohm resistance heater is subject to 110 V of electric supply for 1 minute. How much energy will it provide ? (Select closest answer) 807 kW 807 W 48400 J 48. 4 kJ 48. 4 MJ

48400 J

In a turbine, mass flow rate is 5 kg/s and the change in specific enthalpy is 1500 kJ/kg. What is the power produced by the turbine? .3 kW 300 kW 7500 kW 7.5 kW

7500 kW

When the temperature of a body surface increases from 27 C to 627 C the radiation heat flux emitted by the body will be___ times that of the original radiation heat flux assuming all the factors unchanged. 23.2 81 3 12523 1

81

A laboratory is maintained at 1 cm Mercury vacuum pressure (Pvac). Given the density of Hg to be 13600 kg/m^3 outside pressure of 98 kPa, and g = 9.8 m/s^2 , what is the absolute pressure in the lab?

99.33

For a system to be in equilibrium, it must be simultaneously in thermal, mechanical, and chemical equilibrium. Which of the following is most likely to be in equilibrium? A cup of coffee that has been there for several days A deep - sea exploration capsule navigating in the Pacific Ocean Ice just dropped in a glass of warm tap water Air in a deflating balloon Pasta dropped in boiling water for cooking

A cup of coffee that has been there for several days

Energy inside a controlled volume increases because Energy in the form of heat enters cv Energy in the form of work enters cv Energy carried by mass enters cv Both A & B A, B and C

A, B and C

Entropy is a measure of Chaos Disorganization Randomness All of the above None of the above

All of the above

Turbulence increases when Velocity is higher Absolute viscosity is lower Object size is larger Density is higher All of the above

All of the above

A streamline is: Trajectory of a given flow element Instantaneous trace of all fluid elements passing through a fixed point Any line at a given instant that is tangential to the flow field Trajectory of a well-behaved flow

Any line at a given instant that is tangential to the flow field

Select the FALSE statement A spring is compressed adiabatically, its energy increases Energy transfer by heat occurs as a result of the temperature difference between the system and its surroundings The total energy of a closed system can change as a result of energy transfer across the system boundary by heat and work Based on our class convention heat transfer to a closed system and work done on a closed system are each considered positive: Q>0 and W>0, respectively

Based on our class convention heat transfer to a closed system and work done on a closed system are each considered positive: Q>0 and W>0, respectively

Entropy can be decreased by Heat transfer Mass transfer Irreversibility It can never decrease Both A and B above

Both A and B above

Select the MOST ACCURATE answer For a real process to take place First law must be satisfied Second law must be satisfied First or second law must be satisfied Both first and second laws must be satisfied

Both first and second laws must be satisfied

Coefficient of performance of an ideal refrigerator is Equal to 1 Greater than 1 Less than 1 Can be greater or equal to or less than 1

Can be greater or equal to or less than 1

A reversible and non-adiabatic process always involves ______ in entropy for a closed system Increase Decrease Change No change

Change

How does convection differ from conduction? The rate of heat convection in a given direction is proportional to the temperature gradient in that direction, but in conduction, it is inversely proportional Convection involves fluid motion, whereas conduction does not In convection, magnetic poles attract or repel one another in a similar manner, whereas in conduction, this does not happen Convection is independent of pressure, whereas conduction is not

Convection involves fluid motion, whereas conduction does not

The point at which the liquid and gas phases of a substance become indistinguishable is the Critical point Triple point Saturation point Boiling point

Critical point

A closed system undergoes a cyclic process from state 1, to 2, to 3, to 4, back to state 1. What the difference between its initial temperature, T, and entropy, S and final T and S will be: Delta T = 0 and delta S = 0 Delta T > 0 and delta S = 0 Delta T = 0 and delta S > 0 Delta T = 0 and delta S <0

Delta T = 0 and delta S = 0

In the analogy between electrical circuit and heat transfer problem, the voltage is analogous to ___ and the rate of heat transfer is analogous to ___, respectively. Thermal resistance and electric current Delta T and voltage Voltage and electric current Delta T and electric current Thermal resistance and electric current

Delta T and electric current

For closed systems, which statement is true? Energy can pass it's boundary, but mass cannot Energy cannot pass it's boundary, but mass can Both energy and mass can pass its boundary No energy and mass can pass its boundary

Energy can pass it's boundary, but mass cannot

For a closed system, total energy E, is an _____ property and it consists of kinetic energy, potential energy, and ___ form(s) of energy. Intensive, flow Intensive, other Extensive, flow Extensive, other Extensive, heat

Extensive, other

In a solid, we can have only convection True False

False

Using a device operating in cyclic manner, it is possible to convert all heat energy into work energy (True, False); and it is possible to convert all work energy into heat energy (True, False) True and true True and false False and false False and true

False and true

A cup of hot coffee is left on the table for cooling on its own for a while. The predominant mode of heat transfer is: Conduction Free convection Forced convection Radiation Condensation

Free convection

Area under a curve in the T-S diagram is __________ and P-V diagram is ________ Work and heat Heat and work Energy and area Entropy and work

Heat and work

Consider heat loss through the two walls of a house on a winter night. The walls are identical, except that one of them has a tightly fit glass window. Identify the correct statement in this context. Heat loss through the wall with the glass will be larger Heat loss through the wall with the glass window will be zero Heat loss through both the walls will be the same Heat loss through the wall with the glass window will be smaller

Heat loss through the wall with the glass will be larger

A salesman claims that he has a lawnmower engine that can deliver 2.0 kW mechanical power while using heat at the rate of 4.0 kW. The combustion temperature is 750 K and exhaust (waste heat) is at 400 K. His claim is rather inflated, but possible His claim is quite easily possible because only 2 kW mechanical power is delivered His claim violated first law His claim violated second law

His claim violated second law

The flow visualization method used in the video you just watched was: Dye injection Surface powder Hydrogen bubble Kinetic description

Hydrogen bubble

A fluid flow, in which the density remains constant, is a/an _______ flow Steady Incompressible Subsonic Laminar Internal

Incompressible

As one dives into water in a 10 m deep lake and continues to go down, the pressure on the person ______, and at the bottom of the lake it is very roughly ______ times that on the shore Remains the same, one Increases linearly, two Decreases linearly, .5 Decreases linearly, .1 Increases linearly, 10

Increases linearly, two

In a real process, entropy of a closed system always Decreases Increases Increases only if mass is allowed to cross boundary Increases only if energy is allowed to cross boundary Increases only if energy is NOT allowed to cross boundary

Increases only if energy is NOT allowed to cross boundary

A fan makes us feel cooler in the summer by_____ Increasing the convection heat transfer coefficient of the air Decreasing the convection heat transfer coefficient of the air Decreasing thermal conductivity of our body Increasing thermal conductivity of our body

Increasing the convection heat transfer coefficient of the air

Two objects, X and Y, are identical except that surface of X is intentionally roughened and surface Y is smooth As the speed of airflow passing over the objects is increased from 0 to very high value, the drag force on X will be _______ than that on Y Always greater Always less Initially greater, then smaller Initially smaller, then greater

Initially greater, then smaller

Density if a/an ________ property. Extensive Intensive Intrinsic Process

Intensive

Consider a polytopic process that obeys pv^n = constant. When n = 0, the process is: Isothermal Imposible Isochoric Isobaric

Isobaric

Which of the following is a TRUE statement? Energy can be created It is not possible to completely convert heat from a thermal reservoir to work Reversible process is similar to a cyclic process Energy can be transferred unassisted from a low temperature reservoir to a high temperature reservoir

It is not possible to completely convert heat from a thermal reservoir to work

In an insulated house, a refrigerator is left running with its door open, the room temperature will. . . Remain constant Keep increasing Keep decreasing Depends on whether internal energy is converted into heat

Keep increasing

On a T-v diagram, a fluid that has a quality of x = .7 is in the _____ region. Super critical subcooled/compressed liquid Superheated vapor Liquid + vapor mixture

Liquid + vapor mixture

My weight is 160 pounds. Which of the following is correct about me? M = 160/32 = 5 lbm M = 160 lbm W = 160*32= 5120 lbf All of the above

M = 160 lbm

Thermal conductivity k is a Material property Universal constant Property at a location which depends on flow velocity, shape Property with a value between 0 and 1 None of the above

Material property

When a substance is in gas phase, we apply Ideal Gas equation to calculate properties. True No, we must always use tables True, if we are not given tables Need more information

Need more information

Temperature of a room is raised using an electric heater installed in it. Assuming the room including the electric heater as a single system, the energy input to the system is treated as . . . Positive work Positive heat Negative work - electric energy = work, energy in = negative Negative heat

Negative work - electric energy = work, energy in = negative

A reversible and adiabatic process always involves ________ in entropy for a closed system Increase Decrease Change No change

No change

The weather woman on tv says, "atmospheric pressure is 30.0 inches of mercury and rising" She does not know what she is talking about Pressure cannot be expressed in length units as given above Atmospheric pressure is much much greater than 30.0 inches of mercury All of the above None of the above

None of the above

Units of Reynolds number depend on which quantity? Units of speed Units of viscosity Units of diameter All of the above None of the above

None of the above

The primary dimensionless number used for estimating the convective heat transfer coefficient, h, is ______ Reynolds Number Nusselt Number Prandtl Number Mach Number Convection Number

Nusselt Number

Select the FALSE statement A closed system always contains the same matter; there is no transfer of mass across its boundary The volume of a closed system can change One nanosecond equals 10^9 seconds When a closed system undergoes a process between two specified states, the change in temperature between the end states is independent of details of the process

One nanosecond equals 10^9 seconds

Fluids offer resistance to moving objects. The resistance force is called drag. Drag is a force that acts in the ______ direction of the motion Same Opposite Perpendicular Gravity Upward

Opposite

On a T-v diagram, the state of a fluid that has a quality of x=undefined would be. On the saturated vapor line Outside the vapor dome Need more information Inside the vapor dome

Outside the vapor dome

Among A,B, and C state _______ has the highest temperature and had the highest pressure A and A C and C A and C C and A P and T are equal at A and C

P and T are equal at A and C

For a simple compressible closed system of a pure substance, which of the following will completely define the state of the system? T and V P and v m and T m and P

P and v

In a T-v diagram, slope of a constant pressure will be ___ in the superheated vapor region, and ____ inside the dome. Negative and zero Positive and zero Zero and positive Zero and negative Equal at both

Positive and zero

Imagine you are using a pitot-static probe to measure the speed of your bicycle at sea level. What is the value of the static pressure, P2? Pressure below atmospheric Pressure above atmospheric Pressure equal to atmospheric The stagnation pressure

Pressure equal to atmospheric

The heat transfer coefficient, h, is a Material property Universal constant Property at a location which depends on flow velocity, shape Property with a value between 0 and 1

Property at a location which depends on flow velocity, shape

The sun's energy reaches the earth by ____ A combination of convection and radiation Pure radiation Pure convection Pure conduction

Pure radiation

Assuming other factors remaining unchanged, the air drag on a car is ______ when the speed is doubled Unchanged Doubled Tripled Quadrupled

Quadrupled

For heat conduction in a wall, if the thermal conductivity is doubled and the wall thickness is halved, the thermal resistance will be ___ the original value. The same as Doubled compared to Quadrupled compared to Halved compared to One-fourth of

Quadrupled compared to

The thrust force in an engine is created by _____ Momentum Change in momentum Rate of change of momentum Rate of change of momentum over unit area

Rate of change of momentum

When heat is removed from a system at a constant pressure so that a saturated gas becomes a saturated liquid , the temperature Decreases Increases Remains constant May increase or decrease

Remains constant

A closed system of H2O is at a temperature of 50 deg C and has a specific volume of v = 6.0 m**3/kg. It is in the phase of: Superheated vapor, with a pressure of 12.352 kPa Saturated mixture of liquid and vapor, with a quality of approx., x = 1.0 Saturated vapor, with a pressure of 12.352 kPa Saturated mixture of liquid and vapor, with a quality of approx., x = 0.5 These two are not independent properties, therefore, we need more information

Saturated mixture of liquid and vapor, with a quality of approx., x = 1.0

A closed system of H2O is at a pressure of 75 kPa with u = 1449 kJ/kg. It is in the phase of: Superheated vapor, with a pressure of 120 kPa Saturated mixture of liquid and vapor, with a pressure of 120 kPa Superheated vapor, with a quality, x = 0.5 Saturated mixture of liquid and vapor, with a quality, x = 0.5 These two are not independent properties, therefore, we need more information

Saturated mixture of liquid and vapor, with a quality, x = 0.5

A closed system of H2O is at a temperature of 95 deg C with P = 91.76 kPa. It is in the phase of: Superheated vapor Saturated mixture of liquid and vapor Subcooled vapor Subcooled Liquid These two are not independent properties, therefore, we need more information for determining it's phase or state

Subcooled Liquid

T1 = +10C; T2 = 42F. Which temperature is lower? T1 T2 They are equal Depends on other factors

T2

Diamond is a better heat conductor than silver. True False

True

In forced convection, the fluid is forced to move by external means such as a fan, pump, or the wind. You must provide an answer before moving to the next part. True False

True

In gases and liquids, conduction is due to the collisions of the molecules during their random motion. True False

True

When internal conduction is high compared to the surface heat convection, Biot number is low, and in the limit where Bi is almost zero, the interior temperature may be assumed to be Very high Very low Uniform Linearly increasing from the center to the surface Linearly decreasing from the center to the surface

Uniform

A bus is moving to the right at U mph. You throw a water balloon at the bus (what a prankster you are) at V mph after the bus passes you. A person on the bus sees the balloon hit the bus at U - V V - U V + U V

V - U

Constant density oil flows through a pipe of circular cross section at constant flow mass rate. It enters a section of pipe where cross sectional diameter = d. It exits the pipe where the cross sectional diameter = 2d. What is the relationship between outlet velocity and inlet velocity? Vout = 4Vin Vout = 2Vin Vout = Vin/2 Vout = Vin/4 - m = gamma*A*Vin Vout = Vin

Vout = Vin/4 - m = gamma*A*Vin

A system is taken from State 1 from State 2 in three different ways, W1-2A, W1-2B and W1-2C, as shown below in the PV diagram. Which of the following is true W1-2A= W1-2B = W1-2C W1-2A > W1-2B> W1-2C - area under the curve W1-2A< W1-2B < W1-2C Need equations for P(v)

W1-2A > W1-2B> W1-2C - area under the curve

A wall allows heat conduction through it. When thermal conductivity of the material is doubled, the thickness is tripled, the area is tripled, while keeping other factors unchanged, the amount of heat transfer will ___. Become half Remain the same Will double Will triple Will quadruple

Will double

The thermal conductivity of a material is a measure of how fast heat will be conducted in that material. Yes No

Yes

Units of specific entropy are: kJ/kg kJ/K kJ/kgK kg/K kg/kJK

kJ/kgK

Which of the following lists quantities contains ONLY state functions? Pressure, work, volume and temperature number of mols, volume, heat and enthalpy pressure, number of mols, temperature and internal energy kinetic energy, heat, temperature and work

pressure, number of mols, temperature and internal energy