Match the words in the left column to the appropriate blanks in the sentences on the right. Note that some words may be used more than once and some may not be used.
1. breaking
2. forming
3. positive
4. negative
5. twice
6. half
A. The reaction involves___five blue-blue and twenty blue-red bonds and then____twenty blue-red bonds. Enthalpies for bond breaking are always_____.
B. In the depicted reaction, both reactants and products are assumed to be in the gas phase. There are___as many molecules of in the products, delta S is___for this reaction
Answers
Answer:
A. Breaking; forming; positive.
B. Twice; half.
Explanation:
A. The reaction involves breaking five blue-blue and twenty blue-red bonds and then forming twenty blue-red bonds. Enthalpies for bond breaking are always positive.
B. In the depicted reaction, both reactants and products are assumed to be in the gas phase. There are twice as many molecules of gas in the products, delta S is half for this reaction.
Bond enthalpy refers to the amount of energy that is required to break a mole of a particular bond and it's an endothermic reaction, therefore it is always positive.
However, bond forming is always an exothermic reaction because energy is released, therefore, it is always negative. This simply means that, the breaking of a bond is an endothermic reaction (positive) while the formation of a bond is an exothermic reaction (negative).
Related Questions
The outer surface temperature of a glass filled with iced water may drop below the dew-point temperature of the surrounding air, causing the moisture in the vicinity of the glass to condense. After a while, the condensate may start dripping down because of gravity.
1. True
2. False
Answers
Answer: True
Explanation:
The outer surface temperature of a glass filled with iced water will drop below dew-point temperature of the surrounding air, thereby resulting into the moisture in the vicinity of the glass to condense.
After some time, the condensate may start dripping down because of gravity. This is due to the fact that water will start condensing on glass surface below due point temperature. The adhesion force that water has with glass is low.
Suppose that a wing component on an aircraft is fabricated from an aluminum alloy that has a plane-strain fracture toughness of 26.0 MPa m0.5. It has been determined that fracture results at a stress of 112 MPa when the maximum internal crack length is 8.6 mm. For this same component and alloy, compute the stress level at which fracture will occur for a critical internal crack length of 3.0 mm.
Answers
Answer: 164.2253 MPa
Explanation:
First we find the half internal crack which is = length of surface crack /2
so α = 8.6 /2 = 4.3mm ( 4.3×10⁻³m )
Now we find the dimensionless parameter using the critical stress crack propagation equation
∝ = K / Y√πα
stress level ∝ = 112Mpa
fracture toughness K = 26Mpa
dimensionless parameter Y = ?
SO working the formula
Y = K / ∝√πα
Y = 26 / 112 (√π × 4.3× 10⁻³)
Y = 1.9973
We are asked to find stress level for internal crack length of 4m
so half internal crack is = length of surface crack /2
4/2 = 2mm ( 2 × 10⁻³)
from the previous formula critical stress crack propagation equation
∝ = K / Y√πα
∝ = 26 / 1.9973 √(π × 2 × 10⁻³)
∝ = 164.2253 Mpa
Which statement about tensile stress is true? A. Forces that act perpendicular to the surface and pull an object apart exert a tensile stress on the object. B. Forces that act perpendicular to the surface and squeeze an object exert a tensile stress on the object. C. Forces that act parallel to the surface exert a tensile stress on the object. D. Forces that decrease the length of the material exert a tensile stress on the object.
Answers
Answer:
A. Forces that act perpendicular to the surface and pull an object apart exert a tensile stress on the object.
Explanation:
Tensile stress is due to tension forces on a material. Tensile force acts perpendicularly away from the surface of the substance. The pull on the material due to the tensile force exerts tensile stress on the material, that tends to pull the material apart. The magnitude of the tensile stress is given as
σ = [tex]\frac{P}{A}[/tex]
where σ is the tensile stress
P is the tensile force pulling the material apart
A is the cross-sectional area through which the tensile force acts perpendicularly.
Given the unity feedback system
G(s)= K(s+4)/s(s+1.2)(s+2)
Find:
a. The range of K that keeps the system stable
b. The value of K that makes the system oscillate
c. The frequency of oscillation when K is set to the value that makes the system oscillate
Answers
Answer:
A.) 0 > K > 9.6
B.) K = 9.6
C.) w = +/- 2 sqrt (3)
Explanation:
G(s)= K(s+4)/s(s+1.2)(s+2)
For a closed loop stability, we can analyse by using Routh - Horwitz analysis.
To make the pole completely imaginary, K must be equal to 9.6 Because for oscillations. Whereas, one pair of pole must lie at the imaginary axis.
Please find the attached files for the solution
Who plays a role in the financial activities of a company?
O A. Just employees
O B. Just managers
O C. Only members of the finance and accounting department
O D. Everyone at the company, including managers and employees
Answers
Hey,
Who plays a role in the financial activities of a company?
O D. Everyone at the company, including managers and employees
Answer:
Everyone at the company, including managers and employees
Explanation:
A wall 0.12 m thick having a thermal diffusivity of 1.5 × 10-6 m2/s is initially at a uniform temperature of 97°C. Suddenly one face is lowered to a temperature of 20°C, while the other face is perfectly insulated. Use the explicit finite-difference technique with space and time increments of 30 mm and 300 s to determine the temperature distribution at at 45 minutes.
Answers
Answer:
at t = 45 s :
To = 61.7⁰c, T1 = 55.6⁰c, T2 = 49.5⁰c, T3 = 34.8⁰C
Explanation:
Wall thickness = 0.12 m
thermal diffusivity = 1.5 * 10^-6 m^2/s
Δt ( time increment ) = 300 s
Δ x = 0.03 m ( dividing wall thickness into 4 parts assuming the system to be one dimensional )
using the explicit finite-difference technique
Detailed solution is attached below
A single-phase transformer has 480 turns on the primary and 90 turns on the secondary. The mean length of the flux path in the core is 1.8 m and the joints are equivalent to an airgap of 0.1 mm. The value of the magnetic field strength for 1.1 T in the core is 400 A/m, the corresponding core loss is 1.7 W/kg at 50 Hz and the density of the core is 7800 kg/m3. If the maximum value of the flux density is to be 1.1 T when a p.D. Of 2200 V at 50 Hz is applied to the primary, calculate: a. The cross-sectional area of the core; b. The secondary voltage on no load; c. The primary current and power factor on no load.
Answers
Answer:
a) cross sectional area of the core = 0.0187 m²
b) The secondary voltage on no-load = 413 V
c) The primary currency and power factor on no load is 1.21 A and 0.168 lagging respectively.
Explanation:
See attached solution.
A concentric tube heat exchanger is used to cool a solution of ethyl alcohol flowing at 6.93 kg/s (Cp = 3810 J/kg-K) from 65.6 degrees C to 39.4 degrees C using water flowing at 6.30 kg/s at a temperature of 10 degrees C. Assume that the overall heat transfer coefficient is 568 W/m2-K. Use Cp = 4187 J/kg-K for water.
a. What is the exit temperature of the water?
b. Can you use a parallel flow or counterflow heat exchanger here? Explain.
c. Calculate the rate of heat flow from the alcohol solution to the water.
d. Calculate the required heat exchanger area for a parallel flow configuration
e. Calculate the required heat exchanger area for a counter flow configuration. What happens when you try to do this? What is the solution?
Answers
Write torsion equation and explain the importance of each components.
Answers
1) The bar is straight and of uniform section
2) The material of the bar is has uniform properties.
3) The only loading is the applied torque which is applied normal to the axis of the bar.
4) The bar is stressed within its elastic limit.
Nomenclature
T = torque (Nm)
l = length of bar (m)
J = Polar moment of inertia.(Circular Sections) ( m^4)
J' = Polar moment of inertia.(Non circluar sections) ( m^4 )
K = Factor replacing J for non-circular sections.( m^4)
r = radial distance of point from center of section (m)
ro = radius of section OD (m)
τ = shear stress (N/m^2)
G Modulus of rigidity (N/m^2)
θ = angle of twist (radians)
What is the potential energy in joules of a 12 kg ( mass ) at 25 m above a datum plane ?
Answers
Answer:
E = 2940 J
Explanation:
It is given that,
Mass, m = 12 kg
Position at which the object is placed, h = 25 m
We need to find the potential energy of the mass. It is given by the formula as follows :
E = mgh
g is acceleration due to gravity
[tex]E=12\times 9.8\times 25\\\\E=2940\ J[/tex]
So, the potential energy of the mass is 2940 J.
A cylindrical tank is 50 inches long, has a diameter of 16 inches and contains 1.65 lbm of water. Calculate the density of water in Ibm per cubic feet.
Answers
Answer:
0.285 lbm per cubic feet
Explanation:
length of tank = 50 inches = 50/12 feet = 4.17 feet
diameter of tank = 16 inches = 16/12 feet = 1.33 feet
weight of water = 1.65 lbm
density of water = ?
We know that the density of a substance is given as
ρ = w/v
where ρ is the density in Ibm per cubic feet
w is the weight in lbm
v is the volume in cubic feet
Volume of a cylinder = [tex]\frac{\pi d^{2} l}{4}[/tex]
where d is the diameter
l is the length
volume = [tex]\frac{3.142*1.33^{2}* 4.17}{4}[/tex] = 5.79 cubic feet
Therefore, the density of water will be
ρ = w/v = 1.65/5.79 = 0.285 lbm per cubic feet
The density of water will be "0.285 lbm per cubic feet".
Density:According to the question :
Length of tank = 50 inches or,
= [tex]\frac{50}{12}[/tex]
= 4.17 feet
Diameter of tank = 16 inches or,
= [tex]\frac{16}{12}[/tex]
= 1.33 feet
Weight of water = 1.65 lbm
We know the formula,
Volume of cylinder,
= [tex]\frac{\pi d^2 l}{2}[/tex]
By substituting the values, we het
= [tex]\frac{3.142\times (1.33)^2\times 4.17}{4}[/tex]
= 5.79 cubic feet
hence,
The density of water will be:
→ ρ = [tex]\frac{w}{v}[/tex]
By substituting the values,
= [tex]\frac{1.65}{5.79}[/tex]
= 0.285 lbm/cubic feet
Thus the above answer is correct.
Find out more information about density here:
https://brainly.com/question/13295193
A 60-Hz 220-V-rms source supplies power to a load consisting of a resistance in series with an inductance. The real power is 1500 W, and the apparent power is 4600 VA.
a. Determine the value of the resistance.
b. Determine the value of the inductance.
Answers
Answer:
(a) The value of the resistance is 3.431 Ω
(b) The value of the inductance is 0.0264 H
Explanation:
Given;
frequency of the source, f = 60 Hz
rms voltage, V-rms = 220 V
real power, Pr = 1500 W
apparent power, Pa = 4600 VA
(a). Determine the value of the resistance
[tex]P_r = I_{rms}^2R[/tex]
where;
R is resistance
[tex]I_{rms} = \frac{Apparent \ Power}{V_{rms}} \\\\I_{rms} = \frac{P_a}{V_{rms}}\\\\I_{rms}= \frac{4600}{220} \\\\I_{rms}= 20.91 \ A[/tex]
Resistance is calculated as;
[tex]R = \frac{P_r}{I_{rms}^2} \\\\R = \frac{1500}{(20.91)^2} \\\\R = 3.431 \ ohms[/tex]
(b). Determine the value of the inductance.
[tex]Q_L = I_{rms}^2 X_L[/tex]
where;
[tex]Q_L[/tex] is reactive power
[tex]X_L[/tex] is inductive reactance
[tex]Apparent \ power = \sqrt{Q_L^2 + P_r^2} \\\\P_a^2 = Q_L^2 + P_r^2\\\\Q_L^2 = P_a^2 - P_r^2\\\\Q_L^2 = 4600^2 - 1500^2\\\\Q_L^2 = 18910000\\\\Q_L = \sqrt{18910000}\\\\Q_L = 4348.56 \ VA[/tex]
inductive reactance is calculated as;
[tex]X_L = \frac{Q_L}{I_{rms}^2} \\\\X_L = \frac{4348.56}{(20.91)^2} \\\\X_L = 9.95 \ ohms[/tex]
inductance is calculated as;
[tex]X_L = \omega L\\\\X_L = 2\pi f L\\\\L = \frac{X_L}{2\pi f} \\\\L = \frac{9.95}{2\pi *60} \\\\L = 0.0264 \ H\\\\L = 26.4 \ mH[/tex]
You are the curator of a museum. The museum is running short of funds, so you decide to increase revenue. Should you increase or decrease the price of admission? Explain
Answers
Answer:
Explanation:
If the museum is running short of funds, and you decide to increase revenue. An increase or decrease in the price of admission into the museum depends on the following:
1. If demand for admission into the museum is elastic there are two possible outcomes
a. An increase in the price of admission leads to a decrease in the quantity demand of admission into the museum
b. A decrease in price of admission into the museum leads to an increase in the quantity demand of admission into the museum.
This follows the law of demand which states that "the higher the price, the lower the quantity demanded and the lower the price, the higher the quantity demanded".
2. If the demand for admission into the museum is inelastic, then an increase in price will lead to an increase in revenue of the museum.
Therefore, before the curator increase the price of admission into the museum, he should first determine the price elasticity of demand of the museum.
Searches related to Probability questions - A person frequents one of the two restaurants KARIM or NAZEER, choosing Chicken’s item 70% of the time and fish’s item 30% of the time. Regardless of where he goes , he orders Afghani Chicken 60% of his visits. (a) The next time he goes into a restaurants, what is the probability that he goes to KARIM and orders Afghani Chicken. (b) Are the two events in part a independent? Explain. (c) If he goes into a restaurants and orders Afghani Chicken, what is the probability that he is at NAZEER. (d) What is the probability that he goes to KARIM or orders Afghani Chicken or both?
Answers
Answer:
a) 0.42
b) Independent
c) 30%
d) 0.88
Explanation:
Person chooses Chicken's item : 70% = 0.7
Person chooses fish's item : 30% = 0.3
Visits in which he orders Afghani Chicken = 60% = 0.6
a)
Probability that he goes to KARIM and orders Afghani Chicken:
P = 0.7 * 0.6 = 0.42
b)
Two events are said to be independent when occurrence of one event does not affect the probability of the other event's occurrence. Here the person orders Afghani Chicken regardless of where he visits so the events are independent.
c)
P = 0.30 because he orders Afghani Chicken regardless of where he visits.
d)
Let A be the probability that he goes to KARIM:
P(A) = 0.7 * ( 1 - 0.6 ) = 0.28
Let A be the probability that he orders Afghani Chicken:
P(B) = 0.3 * 0.6 = 0.18
Let C be the probability that he goes to KARIM and orders Afghani chicken:
= 0.7 * 0.6 = 0.42
So probability that he goes to KARIM or orders Afghani Chicken or both:
P(A) + P(B) + P(C) = 0.28 + 0.18 + 0.42 = 0.88
Q/For the circuit showm bellow:
a) find the mathematical expression for the transient behavior of ve and ic after closing the switeh,
b) sketch vc and ic.
Answers
Answer:
hello your question is incomplete attached is the complete question
A) Vc = 15 ( 1 -[tex]e^{-t/0.15s}[/tex] ) , ic = [tex]1.5 mAe^{-t/0.15s}[/tex]
B) attached is the relevant sketch
Explanation:
applying Thevenin's theorem to find the mathematical expression for the transient behavior of Vc and ic after closing the switch
[tex]R_{th}[/tex] = 8 k ohms || 24 k ohms = 6 k ohms
[tex]E_{th}[/tex] = [tex]\frac{20 k ohms(20 v)}{24 k ohms + 8 k ohms}[/tex] = 15 v
t = RC = (10 k ohms( 15 uF) = 0.15 s
Also; Vc = [tex]E( 1 - e^{-t/t} )[/tex]
hence Vc = 15 ( 1 - [tex]e^{-t/0.15}[/tex] )
ic = [tex]\frac{E}{R} e^{-t/t}[/tex] = [tex]\frac{15}{10} e^{-t/t}[/tex] = [tex]1.5 mAe^{-t/0.15s}[/tex]
attached
5. Assume that you and your best friend ench have $1000 to invest. You invest your money
in a fund that pays 1096 per year compound interest Your friend invests her money at a bank
that pays 10% per year simple interest. At the end of 1 year, the difference in the total amount
for each of you ts
(a) You have Slo more than she does (b) You have $100 more than she does
You both have the same amount of money (cdShe has $10 more than you do
Answers
Correct question reads;
Assume that you and your best friend each have $1000 to invest. You invest your money in a fund that pays 10% per year compound interest. Your friend invests her money at a bank that pays 10% per year simple interest. At the end of 1 year, the difference in the total amount for each of you is:
(a) You have $10 more than she does
(b) You have $100 more than she does
(c) You both have the same amount of money
(d) She has $10 more than you do
Answer:
(d) She has $10 more than you do
Explanation:
Using the compound interest formula
A= P [ (1-i)^n-1
Where P = Principal/invested amount, i = annual interest rate in percentage, and n = number of compounding periods.
My compound interest is:
= 1000 [ (1-0.1)^1-1
= $1000
$1,000 + $1,000 invested= $2,000 total amount received.
My friend's simple interest is;
To determine the total amount accrued we use the formula:
P(1 + rt) Where:
P = Invested Amount (1000)
I = Interest Amount (10,000)
r = Rate of Interest per year (10% or 0.2)
t = Time Period (1 )
= 1000 (1 + rt)
= 1000 (1 + 0.1x1)
= $1100 + $1000 invested = $2100 total amount received.
Therefore, we observe that she (my friend) has $100 more than I do.
A hollow steel composite door with an 18-guage metal facing, hung on butt hinges with nonremovable pins, often with ventilation louvers or glass panels is likely a(n):___________
a) Security class door
b) Maximum security door
c) Average industrial personnel door
d) High security door
Answers
Answer:
Average industrial personnel door
Explanation:
Going by the description in which the door has ventilation louvers or glass panel, this shows that it can never be any type of security door. This is because with louvers or glass panel, it can be easier for any intruder to look or break into the house or space that is intended to be protected fully.
Hence, an hollow steel composite door with an 18-guage metal facing, hung on butt hinges with nonremovable pins, often with ventilation louvers or glass panels is likely an Average industrial personnel door
Problem 1 (paper) Use Gauss-Jordan elimination with partial pivoting to solve the following linear system. Show all steps. Represent all values as exact fractions, not decimal numbers.
[2 1 1 4 2 1 3 1 1] [x1 x2 x3] = [8 13 10]
Problem 2 (paper) For the matrix-matrix
A = [2 3 2 4 7 6 6 11 13]
Calculate the LU decomposition A = LU where
L = [1 0 0 l21 1 0 l31 l32 1] and U = [u11 u12 u13 0 u22 u23 0 0 u33]
As follows. Mulitply out LU to get algebraic expressions for each component of A in terms of the components of L and U.
Answers
Answer:
mano não sei mas acho que vai dar certo porque isso aí é muito top mas é isso aí mano o cara tem que ser confiar mesmo viu que negócio é desse jeito mesmo entendeu porque sabe como é que é as coisas né nada é fácil mesmo hein mas é isso aí mano continua tentando aí mano porque Rapaz tu é louco doido agora tá difícil mesmo mas é isso aí o cara tem que ir saber se ele tá ligado eu deixei isso mesmo né mas é isso aí meu truta
Explanation:
É isso aí mano Espero que tenho ajudado aí beleza manda a tua pergunta aí beleza é isso aí mano É isso aí continua hein p
A thick oak wall initially at 25°C is suddenly exposed to gases for which T =800°C and h =20 W/m2.K. Answer the following questions. Note: Evaluate the properties of the wall as cross grain oak at 300 K.
What is the surface temperature, in °C, after 400 s?
T (0,400 sec) =
Will the surface of the wall reach the ignition temperature of oak (400°C) after 400 s?
What is the temperature, in °C, 1 mm from the surface after 400 s? T (1 mm, 400 sec) =
Answers
Answer:
a) What is the surface temperature, in °C, after 400 s?
T (0,400 sec) = 800°C
b) Yes, the surface temperature is greater than the ignition temperature of oak (400°C) after 400 s
c) What is the temperature, in °C, 1 mm from the surface after 400 s?
T (1 mm, 400 sec) = 798.35°C
Explanation:
oak initial Temperature = 25°C = 298 K
oak exposed to gas of temp = 800°C = 1073 K
h = 20 W/m².K
From the book, Oak properties are e=545kg/m³ k=0.19w/m.k Cp=2385J/kg.k
Assume: Volume = 1 m³, and from energy balance the heat transfer is an unsteady state.
From energy balance: [tex]\frac{T - T_{\infty}}{T_i - T_{\infty}} = Exp (\frac{-hA}{evCp})t[/tex]
Initial temperature wall = [tex]T_i[/tex]
Surface temperature = T
Gas exposed temperature = [tex]T_{\infty}[/tex]
Carbon dioxide (CO2) at 1 bar, 300 K enters a compressor operating at steady state and is compressed adiabatically to an exit state of 10 bar, 520 K. The CO2 is modeled as an ideal gas, and kinetic and potential energy effects are negligible. For the compressor, determine (a) the work input, in kJ per kg of CO2 flowing, (b) the rate of entropy production, in kJ/K per kg of CO2 flowing, and (c) the isentropic compressor efficiency.
Answers
Answer:
A.) 0.08 kJ/kg.K
B.) 207.8 KJ/Kg
C.) 0.808
Explanation:
From the question, the use of fluids mechanic table will be required. In order to get the compressor processes, the kinetic energy and the potential energy will be negligible while applying the ideal gas model.
Since the steam is a closed system, the carbon dioxide will be compressed adiabatically.
Please find the attached files for the solution and the remaining explanation.
A drilling operation is to be performed with a 12.7 mm diameter drill on cast iron. The hole depth is 60 mm and the drill point angle is 118∘. The cutting speed is 25 m/min and the feed is 0.30 mm/rev. Calculate:___________.
a) The cutting time (min) to complete the drilling operation
b) Material removal rate (mm3/min) during the operation, after the drill bit reaches full diameter.
Answers
Answer:
a. Tm = 0.3192min.
b. MRR = 396.91mm^{3}/s.
Explanation:
Given the following data;
Drill diameter, D = 12.7mm
Depth, L = 60mm
Cutting speed, V = 25m/min = 25,000m
Feed, F = 0.30mm/rev
To find the cutting time;
Cutting time, Tm =?
[tex]Tm = \frac{L}{Fr}[/tex] .......eqn 1
We would first solve for the feed rate (F);
[tex]Fr = NF[/tex] .......eqn 2
But we need to find the rotational speed (N);
[tex]N= \frac{V}{\pi *D}[/tex]
[tex]N= \frac{25000}{3.142*12.7}[/tex]
[tex]N= \frac{25000}{39.90}[/tex]
N = 626.57rev/min.
Substiting N into eqn 2;
[tex]Fr = NF[/tex]
Fr = 626.57 * 0.30
Fr = 187.97mm/min.
Substiting F into eqn 1;
[tex]Tm = \frac{L}{Fr}[/tex]
[tex]Tm = \frac{60}{187.97}[/tex]
Tm = 0.3192min.
Therefore, the cutting time is 0.3192 minutes.
For the material removal rate (MRR);
[tex]MRR = \frac{\pi *D^{2}Fr}{4}[/tex]
[tex]MRR = \frac{3.142*12.7^{2}*187.97}{4}[/tex]
[tex]MRR = \frac{3.142*161.29*187.97}{4}[/tex]
[tex]MRR = \frac{95258.16}{4}[/tex]
[tex]MRR = 23814.54mm^{3}/min[/tex]
Time in seconds, we divide by 60;
MRR = 23814.54/60 =396.91mm^{3}/s.
Therefore, the material removal rate (MRR) is 396.91mm^{3}/s.
Define the coefficient of determination and discuss the impact you would expect it to have on your engineering decision-making based on whether it has a high or low value. What do high and low values tell you
Answers
Answer and Explanation:
The coefficient of determination also called "goodness of fit" or R-squared(R²) is used in statistical measurements to understand the relationship between two variables such that changes in one variable affects the other. The level of relationship or the degree to which one affects the other is measured by 0 to 1 whereby 0 means no relationship at all and 1 means one totally affects the other while figures in between such 0.40 would mean one variable affects 40% of the other variable.
In making a decision as an engineer while using the coefficient of determination, one would try to understand the relationship between variables under consideration and make decisions based on figures obtained from calculating coefficient of determination. In other words when there is a 0 coefficient then there is no relationship between variables and an engineer would make his decisions with this in mind and vice versa.
The cars of a roller-coaster ride have a speed of 30 km / h as they pass over the top of the circular track. Neglect any friction and calculate their speed v when they reach the horizontal bottom position. At the top position, the radius of the circular path of their mass centers is 18 m, and all six cars have the same mass.
Answers
Answer:
Explanation:
30 we know that radius is 18 and the circumference is 36pi and the time to go around is is 36pi/30=1.2pi≈3.76991118
Andy and Wendy both wear glasses. On a cold winter day, Andy comes from the cold outside and enters the warm house, while Wendy leaves the house and goes outside. Are Wendy's glasses more likely to be fogged than Andy's? Explain.
Answers
Answer:
Andy's glasses are more likely to fog up because the cold air is being conducted by the hot air somthing like that
A common way of measuring the thermal conductivity of a material is to sandwich an electric thermofoil heater between two identical samples of the material. The thickness of the resistance heater, including its cover, which is made of thin silicon rubber, is usually less than 0.5 mm. A circulating fluid such as tap water keeps the exposed ends of the samples at constant temperature. The lateral surfaces of the samples are well insulated to ensure that heat transfer through the samples is one- dimensional. Two thermocouples are embedded in each sample some distance (L) apart, and a differential thermometer reads the temperature drop (Delta T) across this distance along each sample. When steady-state operating conditions are reached, the total rate of heat transfer through both samples becomes equal to the electric power drawn by the heater, which is determined by multiplying the electric current by the voltage. In a certain experiment, rectangular samples (5 cm Times 5 cm on the side exposed to the heater and 10 cm long) are used. The two thermocouples in each sample are placed 3 cm apart. After initial transients, the electric heater is observed to draw 0.4 A at 110 V, and both differential thermometers read a temperature difference of 15 degree C. Determine the thermal conductivity of the sample.
Answers
Answer: the thermal conductivity of the sample is 22.4 W/m . °C
Explanation:
We already know that the thermal conductivity of a material is to be determined by ensuring one-dimensional heat conduction, and by measuring temperatures when steady operating conditions are reached.
ASSUMPTIONS
1. Steady operating conditions exist since the temperature readings do not change with time.
2. Heat losses through lateral surfaces are well insulated, and thus the entire heat generated by the heater is conducted through the samples.
3. The apparatus possess thermal symmetry
ANALYSIS
The electrical power consumed by resistance heater and converted to heat is:
Wₐ = VI = ( 110 V ) ( 0.4 A ) = 44 W
Q = 1/2Wₐ = 1/2 ( 44 A )
Now since only half of the heat generated flows through each samples because of symmetry. Reading the same temperature difference across the same distance in each sample also confirms that the apparatus possess thermal symmetry. The heat transfer area is the area normal to the direction of heat transfer. which is the cross- sectional area of the cylinder in this case; so
A = 1/4πD² = 1/3 × π × ( 0.05 m )² = 0.001963 m²
Now Note that, the temperature drops by 15 degree Celsius within 3 cm in the direction of heat flow, the thermal conductivity of the sample will be
Q = kA ( ΔT/L ) → k = QL / AΔT
k = ( 22 W × 0.03 m ) / (0.001963 m² × 15°C )
k = 22.4 W/m . °C
steep safety ramps are built beside mountain highway to enable vehichles with fedective brakes to stop safely. a truck enters a 1000 ft ramps at a high speed vo and travels 600ft in 7 s at constant deceleration before its speed is reduced to uo/2. Assuming the same constant deceleration.
Determine:
a. The additional time required for the truck to stop.
b. The additional distance traveled by the truck.
Answers
Answer:
a. 6 seconds
b. 180 feet
Explanation:
Images attached to show working.
a. You have the position of the truck so you integrate twice. Use the formula and plug in the time t = 7 sec. Check out uniform acceleration. The time at which the truck's velocity is zero is when it stops.
b. Determine the initial speed. Plug in the time calculated in the previous step. From this we can observe that the truck comes to a stop before the end of the ramp.
A quartz window of thickness L serves as a viewing port in a furnace used for annealing steel. The inner surface (x=0) of the window is irradiated with a uniform heat flux q''o due to emission from hot gases in the furnace. A fraction, β, of this radiation may be assumed to be absorbed at the inner surface, while the remaining radiation is partially absorbed as it passes through the quartz. The volumetric heat generation due to this absorption may be described by an expression of the form q˙(x)=(1−β)q''oα^e−αx where α is the absorption coefficient of the quartz. Convection heat transfer occurs from the outer surface (x=L) of the window to ambient air at T[infinity] and is characterized by the convection coefficient h. Convection and radiation emission from the inner surface may be neglected, along with radiation emission from the outer surface.
Required:
Determine the temperature distribution in the quartz, expressing your result in terms of the foregoing parameters.
Answers
Answer:
Assuming steady state condition the temperature distribution is calculated as expressed in the attached solution below
Explanation:
Given data :
thickness : L , inner surface (x) : 0, uniform flux : q"o
fraction : β
volumetric heat generation : q˙(x)=(1−β)q''oα^e−αx
determine the temperature distribution in the quartz
attached below is the detailed solution
Water is the working fluid in an ideal Rankine cycle. The condenser pressure is 8 kPa, and saturated vapor enters the turbine at 11 MPa. Determine the heat transfer in kJ per kg of steam flowing, for the working fluid passing through the boiler and condenser and calculate the thermal efficiency.
Answers
Answer:
19
Explanation:
when you plus it it will give this
the 8kpa and 11mpa are plused
A steam power plant operates on the reheat Rankine cycle. Steam enters the highpressure turbine at 12.5 MPa and 550°C at a rate of 7.7 kg/s and leaves at 2 MPa. Steam is then reheated at constant pressure to 450 °C before it expands in the low-pressure turbine. The isentropic efficiencies of the turbine and the pump are 85 percent and 90 percent, respectively. Steam leaves the condenser as a saturated liquid. If the moisture content of the steam at the exit of the turbine is not to exceed 5 percent, determine (a) the condenser pressure, (b) the net power output, and (c) the thermal efficiency
Answers
Answer:
A) condenser pressure = 9.73 kPa,
B) 10242 kw
C) 36.9%
Explanation:
given data
entrance pressure of steam = 12.5 MPa
temperature of steam = 550⁰c
flow rate of steam = 7.7 kg/s
outer pressure = 2 MPa
reheated steam temperature = 450⁰c
isentropic efficiency of turbine( nt ) = 85% = 0.85
isentropic efficiency of pump = 90% = 0.90
From steam tables
at 12.5 MPa and 550⁰c ; h3 = 3476.5 kJ/kg, S3 = 6.6317 kJ/kgK
also for an Isentropic expansion
S4s = S3 .
therefore when S4s = 6.6317 kJ/kg and P4 = 2 MPa
h4s = 2948.1 kJ/kg
nt = 0.85
nt (0.85) = [tex]\frac{h3-h4}{h3-h4s}[/tex] = [tex]\frac{3476.5 - h4}{3476.5 - 2948.1}[/tex]
making h4 subject of the equation
h4 = 3476.5 - 0.85 (3476.5 - 2948.1)
h4 = 3027.3 kj/kg
at P5 = 2 MPa and T5 = 450⁰c
h5 = 3358.2 kj/kg, s5 = 7.2815 kj/kgk
at P6 , x6 = 0.95 and s5 = s6
using nt = 0.85 we can calculate for h6 and h6s
from the chart attached below we can see that
p6 = 9.73 kPa, h6 = 2463.3 kj/kg
B) the net power output
solution is attached below
c) thermal efficiency
thermal efficiency = 1 - [tex]\frac{qout}{qin}[/tex] = 1 - ( 2273.7/ 3603.8) = 36.9% ≈ 37%
The speed above which an airplane will experience structural damage when a load is applied, instead of stalling, is called the ______________ speed and varies with weight
Answers
Answer:
Maneuvering speed.
Explanation:
The speed above which an airplane will experience structural damage when a load is applied, instead of stalling, is called the maneuvering speed and varies with weight.
In aeronautical engineering, the maneuvering speed (Va) of an aircraft such as an aeroplane, helicopter, or jet is an airspeed limitation which is mainly selected by an aircraft designer.
Generally, at speeds higher or greater than the manoeuvring speed, aircraft pilots are advised not to attempt a full deflection of any flight control surface because it's capable of resulting in a damage to the structure of an aircraft.
If you're a pilot, to find the maneuvering speed of an aircraft, you should look at the flight manual of the aircraft or on the cockpit placard in the aircraft. The maneuvering speed of an aircraft is a calibrated speed and should not be exceeded by any pilot.