1st Year: May exam

Question 1

First Law of Thermodynamics:

Answer 1

Q − W = ∆U + ∆KE + ∆P E + ∆SE

Question 2

First Law of Thermodynamics for a cyclic process

Answer 2

∑Q = ∑W

Question 3

Equation of state for a perfect gas

Answer 3

P V = mRT

or

P = ρRT

Question 4

Change in internal energy:

Answer 4

∆U = mCv∆T

Question 5

Change in enthalpy:

Answer 5

∆H = mCp∆T

Question 6

Isothermal Process

Answer 6

Constant Temperature

Process Path: P V = C
Work: W = mRTln(V2/V1)

Question 7

Adiabatic Process

Answer 7

No Heat Transfer
Q=0
Process Path: P V ^γ = C
Work: W =(P1V1 − P2V2)/γ − 1

Question 8

Polytropic Process

Answer 8

Process Path: P V ^n = C

Work: W =(P1V1 − P2V2)/n-1

Question 9

Relating ratios of T, V, and P…

Answer 9

T2/T1 = (V1/V2)^γ−1 = (P2/P1)^y-1/y

change γ to n for polytropic processes

Question 10

y =

Answer 10

Cp/Cv

normally equals 1.4

Question 11

R =

Answer 11

Cp - Cv

Question 12

Cv =

Answer 12

R / y-1

Question 13

Cp =

Answer 13

R*y / y-1

Question 14

Constant Pressure Process: Q=

Answer 14

mCp∆T

Question 15

Mass flow rate

Answer 15

m* = VAρ

Question 16

Volume flow rate

Answer 16

Q = AV

Question 17

Bernoulli’s equation

Answer 17

P1/ρ + V1^2/2 + gZ1 = P2/ρ + V2^2/2 + gZ2

Question 18

First Law of Thermodynamics for a Closed process

Answer 18

Q-W=∆U

more specifically:
Q-(Wshaft +Wdisp)=∆U

Question 19

Units of Volume flow rate:

Answer 19

m^3/s

Question 20

Units of Mass flow rate

Answer 20

Kg/s

Question 21

Effect of nozzle on tube opening

Answer 21

Are decreases so velocity increases as flow rate constant.

Question 22

What does a steady flow process mean?

Answer 22

Flow RATE constant. ie Q or M

Not necessarily velocity constant

Question 23

What is Guage pressure?

Answer 23

The amount the pressure is over atmospheric.

Question 24

What is Vacuum pressure

Answer 24

The amount the pressure is under atmospheric.

Question 25

How do you find buoyancy force?

Answer 25

F=ρg∆hA

Question 26

Work done by power source:

Answer 26

W = Pt

Question 27

What is enthalpy?

Answer 27

H = U +PV

Question 28

Equation for constant pressure process (piston with weight)

Answer 28

Q = ∆H = mCp∆T

Question 29

How to find n where y=x^n

Answer 29

n=log.x(y)

Question 30

For collision question:

Answer 30

• W = ∆U +∆Ek
• Patmos(∆V) = cm∆T +1/2m∆V^2

Clever subs include: T=PV/mR Cv/R = 1/y-1

Question 31

For mixing gasses/liquids question:

Answer 31

U1=U2

U1 = (cmT1)a + (cmT1)b + ..etc

U2 = c(ma + mb +…etc)T2

Question 32

What Is an isolated system?

Answer 32

No interaction with surroundings

Q=0 W=0

Question 33

What Is a Reversible process?

Answer 33

Energy can be constantly converted without loosing any. Like a pendulum with no friction. (Never occurs in real life)

Question 34

What is an Irreversible process?

Answer 34

Friction acts on system converting energy to heat which cant convert back. Eventually brings system to hault