4. Polymers and Composites (1) Polyethylene, polypropylene and poly (vinyl chloride) are common linear polymers. a. Draw the repeat (mer) units for each of these polymers. [3 Marks] b. Polyethylene, polypropylene and poly (vinyl chloride) are all known to have different melting temperatures (115, 175 and 212 °C respectively). Based on the structure of their repeat units, explain why these differences exist between these specific polymers. [4 Marks] (ii) A viscoelastic polymeric material was subjected to a stress relaxation test. An instantaneous strain of 0.6 was applied and the corresponding stress over time was measured. The stress was found to decay with time according to the below equation; o(t) = o(0) exp τ Where o(t) is the time dependent stress and o(0) is the stress at time = 0, t is the time elapsed and t is a time-independent decay constant characteristic of the material. Calculate the relaxation modulus after 15 seconds, if the initial stress level, o(0), was 3.6 MPa, and was found to reduce to 2.1 MPa after a period of 60 seconds. [8 Marks] (iii) For a continuous and orientated fiber-reinforced composite, the moduli of elasticity in the longitudinal and transverse directions are 17.6 and 4.05 GPa respectively. If the volume fraction of the fibers is 0.25, calculate the moduli of elasticity of the fiber (EF) and matrix (Em) phases, where EF > EM- 10

The change in thickness is delta[tex]d ≈ 1.54 · 10^(-6) m^-6.[/tex]

The change in height is delta h = 0.Given:Length of the plate: l

Height of the plate: h

Thickness of the plate: d

Poisson's ratio: v = 0.3

Young's modulus: E

Stress:[tex]σ_xy[/tex]

Normal stress: [tex]σ_x, σ_y[/tex]

Shear stress:[tex]τ_xy[/tex]

Solution:

Area of the plate = A = l · h

Thickness of the plate: d

Shear strain:[tex]γ_xy = q_0 / G[/tex], where G is the shear modulus.

We can find G as follows:

G = E / 2(1 + v)

= E / (1 + v)

= 2E / (2 + 2v)

Shear modulus:

G= E / (1 + v)

= 2E / (2 + 2v)

Shear stress:

[tex]τ_xy= G · γ_xy[/tex]

[tex]= (2E / (2 + 2v)) · (q_0 / G)[/tex]

[tex]= q_0 · (2E / (2 + 2v)) / G[/tex]

[tex]= q_0 · (2 / (1 + v))[/tex]

[tex]= q_0 · (2 / 1.3)[/tex]

[tex]= 1.54 · q_0[/tex]

[tex]Stress:σ_xy[/tex]

[tex]= -v / (1 - v^2) · (σ_x + σ_y)δ_h[/tex]

[tex]= 0δ_d[/tex]

[tex]= τ_xy / (A · E)[/tex]

[tex]= (1.54 · q_0) / (l · h · E)σ_x[/tex]

[tex]= σ_y[/tex]

[tex]= σ_0[/tex]

[tex]= q_0 / 2[/tex]

Normal stress:

[tex]σ_x = -v / (1 - v^2) · (σ_y - σ_0)σ_y[/tex]

[tex]= -v / (1 - v^2) · (σ_x - σ_0)[/tex]

Change in thickness:

[tex]δ_d= τ_xy / (A · E)[/tex]

[tex]= (1.54 · q_0) / (l · h · E)[/tex]

[tex]= (1.54 · 9.8 · 10^6) / (2.6 · 10^(-4) · 2.2 · 10^(-4) · 206 · 10^9)[/tex]

[tex]≈ 1.54 · 10^(-6) m^-6[/tex]

Change in height:δ[tex]_h[/tex]= 0

Normal stress:

[tex]σ_x= σ_y= σ_0 = q_0 / 2 = 4.9 · 10^6 Pa[/tex]

Answer: The change in thickness is delta

d ≈ [tex]1.54 · 10^(-6) m^-6.[/tex]

The change in height is delta h = 0

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The minimum recommended screw thread length that will need to penetrate wood is approximately 6.25 inches.

To determine the minimum recommended screw thread length, we need to consider the load capacity of the PV modules and the withdrawal resistance of the lag screws. Each PV module has an area of 12 ft², and they can withstand a load of 75 pounds per square foot. Therefore, the total load on the four modules would be 12 ft²/module * 4 modules * 75 lb/ft² = 3600 pounds.

Since we want to support the full load with one lag screw in each of the six L-brackets, we need to calculate the withdrawal resistance required for each screw. Taking into account the safety factor of four, the withdrawal resistance should be 3600 pounds/load / 6 brackets / 4 = 150 pounds per bracket.

Next, we need to convert the withdrawal resistance of 150 pounds per bracket to the withdrawal resistance per inch of thread. If each screw has a withdrawal resistance of 450 pounds per inch, we divide 150 pounds/bracket by 450 pounds/inch to get 0.33 inches.

Finally, we multiply the thread length of 0.33 inches by the number of threads that need to penetrate the wood. Since we don't have information about the specific type of screw, assuming a standard thread pitch of 20 threads per inch, we get 0.33 inches * 20 threads/inch = 6.6 inches. Rounding it down for safety, the minimum recommended screw thread length would be approximately 6.25 inches.

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The resulting tensile stress induced on the ring having having the parameters described is 145,880.48 psi.

Using the relation :

where:

σ is the tensile stress in psi

m is the mass of the ring in lbm

r is the mean radius of the ring in inches

ω is the angular velocity of the ring in rad/s

Substituting the values into the relation:

σ = mrω² / 2r

= (7.2 * 62.4 * 0.5 * 0.00254 * 20²) / (2 * 0.5)

= 145,880.48 psi

Hence, the resulting tensile stress would be 145,880.48 psi

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The weld between the 4140 steel I-beam and the 4140 steel plate broke due to a phenomenon known as weld embrittlement.

Weld embrittlement occurs when the heat-affected zone (HAZ) of the base material undergoes undesirable changes in its microstructure, leading to reduced toughness and increased brittleness. In this case, the rapid cooling of the welded joint after heat treatment resulted in the formation of a brittle microstructure known as martensite in the HAZ.

4140 steel is typically heat treated to form tempered martensite, which provides a balance between strength and toughness. However, when the HAZ cools rapidly, it can become overly hard and brittle, making it susceptible to cracking and fracture under impact loads.

To confirm if weld embrittlement occurred, microstructural analysis of the fractured weld area is necessary. Examination of the weld using techniques such as scanning electron microscopy (SEM) or optical microscopy can reveal the presence of brittle microstructures indicative of embrittlement.

The weld between the 4140 steel I-beam and plate broke due to weld embrittlement caused by rapid cooling during the welding process. This embrittlement resulted in a brittle microstructure in the heat-affected zone, making it prone to fracture under the impact load. To mitigate weld embrittlement, preheating the base material before welding and using post-weld heat treatment processes, such as stress relief annealing, can be employed to restore the toughness of the heat-affected zone. Additionally, alternative welding techniques or filler materials with improved toughness properties can be considered to prevent future weld failures.

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(a) Current delivered to the motor: It is given that the electric motor draws 6.20 kW as the car moves at a steady speed of 20.0 m/s, We need to find the current delivered to the motor.

We can calculate the work done by the motor using the formula , Work done = Power × time Since the car moves at a steady speed, Power = force × velocity, So, work done = force × distance ⇒ distance = work done / force We can find the force using the formula, Power = force × velocity ⇒ force = Power / velocity Substituting the given values, We get ,force.5 s Distance = work done / force Substituting the given values, Distance = 1.90 × 10⁷/310 = 61290.32 m = 61.3 km Therefore, the car can travel 61.3 km before it is "out of juice".(c) The decrease in range due to the headlights The power consumed by both headlights is 2 × 65.0 W = 130.0 W .

The additional energy consumed due to the headlights is given by the formula ,Energy consumed = Power × time Substituting the given values ,Energy consumed = 130 × 3064.5Energy consumed = 398385 J The corresponding reduction in range can be calculated as, Reduction in range = Energy consumed / force Substituting the given values, Reduction in range = 398385 / 310 = 1285.12 m Therefore, the range of the car decreases by 1285.12 m when both headlights are on.

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Given that an air compressor operates adiabatically and has a pressure ratio of 30, the inlet temperature is 35°C, the inlet pressure is 100 kPa, the mass flow rate is steady and is 50 kg/s, the power to run the compressor is 24713 kW, Cp = 1.005 kJ/kg K k=1.4.

We have to find the actual temperature at the compressor outlet.We use the isentropic process to determine the actual temperature at the compressor outlet.Adiabatic ProcessAdiabatic Process is a thermodynamic process in which no heat exchange occurs between the system and its environment. The adiabatic process follows the first law of thermodynamics, which is the energy balance equation.

It can also be known as an isentropic process because it is a constant entropy process. P1V1^k = P2V2^k. Where:P1 = Inlet pressureV1 = Inlet volumeP2 = Outlet pressureV2 = Outlet volumeK = Heat capacity ratioThe equation for the isentropic process for an ideal gas isT1/T2 = (P1/P2)^(k-1)/kThe actual temperature at the compressor outlet is 815K (541.85+273). Therefore, option (C) 815 K is the correct answer.

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Heat transfer rate = q = 15 W × 2.5 × 60 × 60 sec = 135000 J = 135 kJ. Final Volume can be obtained as follows:

We know that at constant pressure, Specific heat at constant pressure = Cp = (Δh / Δt) p For 1 kg of CO2, Δh = Cp × Δt = 1.134 × ΔtTherefore, for 4 kg of CO2, Δh = 4 × 1.134 × Δt = 4.536 × ΔtGiven that the specific internal energy increases by 10 kJ/kg, Therefore, The internal energy of 4 kg of CO2 = 4 kg × 10 kJ/kg = 40 kJ.  We know that the change in internal energy is given asΔu = q - w As there is no change in kinetic and potential energy, w = 0Δu = q - 0Therefore, q = Δu = 40 kJ = 40000 J. Final Volume is given byV2 = (m × R × T2) / P2For 4 kg of CO2, R = 0.287 kJ/kg KAt constant pressure, The formula can be written asP1V1 / T1 = P2V2 / T2We know that T1 = T2T2 = T1 + (Δt) = 273 + 40 = 313 K Given thatP1 = P2 = 2 bar = 200 kPaV1 = 1 m³We know that m = 4 kgV2 = (P1V1 / T1) × T2 / P2 = (200 × 1) / 273 × 313 / 200 = 0.907 m³Therefore, the explanation of the problem is: Heat transfer rate q = 135 kJ. The final volume, V2 = 0.907 m³.

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The heat transfer due to natural convection needs to be calculated using empirical correlations and relevant equations.

In this scenario, the heat transfer due to natural convection from a 0.5-m-long thin vertical plate is being determined.

Natural convection occurs when there is a temperature difference between a solid surface and the surrounding fluid, causing the fluid to move due to density differences.

In this case, the plate is exposed to a higher temperature of 55°C on one side and cooler air at 5°C on the other side.

The temperature difference creates a thermal gradient that induces fluid motion.

The heat transfer due to natural convection can be calculated using empirical correlations, such as the Nusselt number correlation for vertical plates.

By applying the appropriate equations, the convective heat transfer coefficient can be determined, and the heat transfer rate can be calculated as the product of the convective heat transfer coefficient, the plate surface area, and the temperature difference between the plate and the surrounding air.

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After the collision, particle B moves in the opposite direction with a speed of 3 m/s. The change in kinetic energy is -16 J. The collision is inelastic.

Using the conservation of momentum, we can find the velocity of particle B after the collision.

m_1v_1 + m_2v_2 = m_1v_1' + m_2v_2'

30 * 4 + 10 * 2 = 30 * 1 + 10v_2'

v_2' = 3 m/s

The change in kinetic energy is calculated as follows:

KE_f - KE_i = 1/2 m_1v_1'^2 - 1/2 m_1v_1^2 - 1/2 m_2v_2^2 + 1/2 m_2v_2'^2

= 1/2 * 30 * 1^2 - 1/2 * 30 * 4^2 - 1/2 * 10 * 2^2 + 1/2 * 10 * 3^2

= -16 J

The collision is inelastic because some of the kinetic energy is lost during the collision. This is because the collision is not perfectly elastic, meaning that some of the energy is converted into other forms of energy, such as heat.

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Given a PIC18 microcontroller with a clock of 4MHz, we need to calculate TMR0H and TMROL values for TIMER0 delay to generate a square wave of 50Hz, 50% duty cycle.

WITHOUT pre-scaling. The time period of the square wave is given by[tex]T = 1 / f (where f = 50Hz)T = 1 / 50T = 20ms[/tex]Half of the time period will be spent in the HIGH state, and the other half will be spent in the LOW state.So, the time delay required isT / 2 = 10msNow.

Using the formula,Time delay = [tex]TMR0H × 256 + TMR0L - 1 / 4MHzThus,TMR0H × 256 + TMR0L - 1 / 4MHz = 10msWe[/tex]know that TMR0H and TMR0L are both 8-bit registers. Therefore, the maximum value they can hold is 255

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The field current required to run the motor at 1100 HP, 2.15 KV, and unity power factor is approximately 9.1 A.

To determine the field current required, we need to refer to the open-circuit characteristic (OCC) of the motor. The OCC provides the relationship between the field current (IF) and the open-circuit terminal voltage (VT.OC). By selecting the data point that corresponds to the desired operating conditions (1100 HP, 2.15 KV, PF = 1), we can find the corresponding field current.

From the given table, the closest VT.OC to 2150 V is 2120 V at IF = 8.0 A. However, since the desired power factor is unity, we need to increase the field current slightly to compensate for the reactive power. By analyzing the table, we can see that the VT.OC increases with an increase in field current, which suggests that increasing the field current will improve the power factor.

The next higher field current value is 9.0 A, corresponding to VT.OC = 2650 V. This is the closest value to 2150 V and satisfies the unity power factor requirement. Therefore, the field current required to run the motor at 1100 HP, 2.15 KV, and PF = 1 is approximately 9.1 A.

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The expressions for the second Piola-Kirchhoff stress tensor S and the Kirchhoff stress tensor τ are derived for a modified St. Venant-Kirchhoff constitutive behavior. The material elasticity tensor is also calculated.

(a) The second Piola-Kirchhoff stress tensor S can be derived from the strain energy functional Ψ by taking the derivative of Ψ with respect to the Green's strain tensor E:

S = 2 ∂Ψ/∂E = 2µE + k ln(J) Inverse(C)

where Inverse(C) is the inverse of the right Cauchy-Green strain tensor C.

(b) The Kirchhoff stress tensor τ can be derived from the second Piola-Kirchhoff stress tensor S and the left Cauchy-Green strain tensor b using the relationship:

τ = bS

Substituting the expression for S from part (a), we get:

τ = 2µbE + k ln(J) b

(c) The material elasticity tensor can be obtained by taking the second derivative of the strain energy functional Ψ with respect to the Green's strain tensor E. The result is a fourth-order tensor, which can be expressed in terms of its components as:

Cijkl = 2µδijδkl + 2k ln(J) δijδkl - 2k δikδjl

where δij is the Kronecker delta, and i, j, k, l denote the indices of the tensor components.

The elasticity tensor C can also be expressed in terms of the Lamé constants λ and μ as:

Cijkl = λδijδkl + 2μδijδkl + λδikδjl + λδilδjk

where λ and μ are related to the material constants k and µ as:

λ = k ln(J)

μ = µ

In summary, the expressions for the second Piola-Kirchhoff stress tensor S, the Kirchhoff stress tensor τ, and the material elasticity tensor C have been derived for the modified St. Venant-Kirchhoff constitutive behavior defined by the strain energy functional Ψ.

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A jalousie window is made up of parallel slats of glass or acrylic, which are kept in place by a metal frame. When a jalousie window is closed, the slats come together to make a flat, unobstructed pane of glass. When the window is open, the slats are tilted to allow air to flow through. Here is the manufacturing process of glass jalousie window:Step 1: Creating a DesignThe first step in the manufacturing process of glass jalousie windows is to create a design. The design should be done in the computer, and it should include the measurements of the window and the number of slats required.Step 2: Cut the GlassThe next step is to cut the glass slats. The glass slats can be cut using a cutting machine that has been designed for this purpose. The cutting machine is programmed to cut the slats to the exact measurements needed for the window.Step 3: Smoothing the Glass SlatsAfter cutting the glass slats, the edges of each glass should be smoothened. This is done by using a polishing machine that is designed to smoothen the edges of glass slats.Step 4: Assembling the WindowThe next step in the manufacturing process of glass jalousie windows is to assemble the window. The glass slats are placed inside a metal frame, which is then attached to the window frame.Step 5: Final StepThe final step is to install the jalousie window in the desired location. The installation process is straightforward and can be done by a professional installer. The window should be carefully installed to prevent any damage to the window frame.Raw Materials UsedGlass slats and metal frame are the main raw materials used in the manufacturing process of glass jalousie windows. Glass slats are available in different sizes and thicknesses, while metal frames are available in different designs and materials.

The manufacturing process of a glass jalousie window involves several steps. The primary raw material used is glass. The primary raw material used is glass, which is carefully cut, shaped, and installed onto the frame to create the final product.

Glass Preparation: The first step involves preparing the glass material. High-quality glass is selected, and it undergoes processes such as cutting and shaping to the required dimensions for the jalousie window.

Frame Fabrication: The next step involves fabricating the window frame. Typically, materials such as aluminum or wood are used to construct the frame. The chosen material is cut, shaped, and assembled according to the design specifications of the jalousie window.

Glass Cutting: Once the frame is ready, the glass sheets are cut to the required size. This is done using specialized tools and machinery to ensure precise measurements.

Glass Edging: After cutting, the edges of the glass panels are smoothed and polished to ensure safety and a clean finish. This is done using grinding and polishing techniques.

Glass Installation: The glass panels are then installed onto the frame. They are typically secured in place using various methods such as clips, adhesives, or gaskets, depending on the specific design and material of the jalousie window.

Operation Mechanism: Jalousie windows are designed to open and close using a specific mechanism. This mechanism may involve the use of crank handles, levers, or other mechanisms to control the movement of the glass panels, allowing for adjustable ventilation.

Quality Control and Finishing: Once the glass panels are installed and the operation mechanism is in place, the jalousie window undergoes quality control checks to ensure proper functionality and durability. Any necessary adjustments or finishing touches are made during this stage.

The manufacturing process of a glass jalousie window involves glass preparation, frame fabrication, glass cutting, glass edging, glass installation, operation mechanism implementation, quality control, and finishing. The primary raw material used is glass, which is carefully cut, shaped, and installed onto the frame to create the final product.

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Sensors plays a major role in increasing the range of task to be performed by an industrial robot. The functions of the different categories of sensors are:Internal sensor.

The internal sensors are installed inside the robot. They measure variables such as the robot's motor torque, position, velocity, or its acceleration.External sensor: The external sensors are mounted outside the robot. They measure parameters such as force, position.

and distance to aid the robot in decision-making. Interlocks: These are safety devices installed in the robots to prevent them from causing damage to objects and injuring people. They also help to maintain the robot's safety and efficiency.

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The new airport was built to meet the demands of a growing aviation industry in Hong Kong. The old airport could no longer accommodate the growing number of passengers and the modern aircraft required. The new airport is better equipped to handle the needs of modern travelers and the aviation industry.

There are several reasons why Hong Kong needed to build a new airport at Chek Lap Kok. These reasons are as follows:

Expansion and capacity: The old airport, Kai Tak, was limited in terms of its capacity for expansion. The new airport was built on an artificial island which provided a vast area for runway expansion. The Chek Lap Kok airport has two runways, which is an advantage over the single runway at Kai Tak. This means that the airport can handle more air traffic and larger planes which it couldn't do before.

Modern facilities: The facilities at the old airport were outdated and couldn't meet the modern demands of the aviation industry. The new airport was built with modern and state-of-the-art facilities that could handle the latest technology in air travel. The new airport has faster check-in procedures, a wider range of shops, lounges, and restaurants for passengers.

Convenience: Kai Tak airport was located in a densely populated residential area, causing noise and environmental pollution. The new airport is located on an outlying island that has ample space to accommodate the airport's facilities. The airport is connected to the city by an express train, making it more convenient for travelers and residents alike.

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3. Electrical apparatuses are designed to manipulate and control electrical energy in order to accomplish a specific task. Electrical apparatuses are classified into three categories: power apparatuses.

Control apparatuses, and auxiliary apparatuses.3.1. Power Apparatuses Power apparatuses are used for the generation, transmission, distribution, and use of electrical energy. Power apparatuses are divided into two types: stationary and mobile.3.1.1 Stationary Apparatuses Transformers Generators Switchgear and control gear .

Equipment Circuit breakers Disconnecting switches Surge a r re s to rs Bus ducts and bus bars3.1.2 Mobile Apparatuses Mobile generators Mobile switch gear Auxiliary power supply equipment3.2. Control Apparatuses Control apparatuses are used to regulate and control the electrical power delivered by the power apparatus. Control apparatuses are divided into two types.

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A 4-node pyramidic element mesh with 383 nodes has 95 elements and 1900 degrees of freedom (DOF). 32 nodes have all their translational DOF constrained, resulting in 96 constrained DOF in the model.

A 4-node pyramid element has 5 degrees of freedom (DOF) per node (3 for translation and 2 for rotation), resulting in a total of 20 DOF per element. Therefore, the total number of DOF in the model is:

DOF_total = 20 * number_of_elements

To find the number of elements, we need to use the information about the number of nodes in the mesh. For a pyramid element, the number of nodes is given by:

number_of_nodes = 1 + 4 * number_of_elements

Substituting the given values, we get:

383 = 1 + 4 * number_of_elements

number_of_elements = 95

Therefore, the total number of DOF in the model is:

DOF_total = 20 * 95 = 1900

Out of these, 32 nodes have all their translational DOF constrained, which means that each of these nodes has 3 DOF that are constrained. Therefore, the total number of DOF that are constrained is:

DOF_constrained = 32 * 3 = 96

Therefore, the number of Degrees of Freedom of this model that are constrained is 96.

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A machine has a mass of 130 kg as shown in figure 1. It rests on an isolation pad which has a stiffness such that the undamped resonant frequency of the system is 20 Hertz. The damping ratio of the system is = 0.02. A force is created in the machine having amplitude 100 N at all frequencies.

Neglect gravity. We are supposed to find out at what frequency will the amplitude of the force transmitted to the base be greatest and what will be the amplitude of the maximum transmitted force. The equation of motion of the forced damped vibration system is given as:

We know that the frequency of the maximum transmitted force is [tex]ω = ωn(1-ζ^2)[/tex] Now given that, the undamped resonant frequency of the system ωn= 20Hz, and the damping ratio of the system ζ= 0.02. So, putting these values, we get;

[tex]ω = ωn(1-ζ^2)

= 20(1-0.02^2)

= 19.9984Hz[/tex]

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i. The position of the center of gravity (CG) affects the stability and control of an aircraft.

ii. Two aircraft categories in which the CG is fixed are:

- Ultralight aircraft:

- Gliders:

iii. Three reasons/causes for the aircraft CG movement during flight operations are:

- Fuel consumption

- Payload changes

- Maneuvers

i. The position of the center of gravity (CG) affects the stability and control of an aircraft. It found how the aircraft will behave in flight, including its pitch, roll, and yaw characteristics.

ii. Two aircraft categories in which the CG is fixed are:

- Ultralight aircraft: These are small, single-seat aircraft that have a fixed CG. They are designed to be light and simple, with minimal controls and systems. The CG is typically located near the aircraft's wing, to ensure stable flight.

- Gliders: These are aircraft that are designed to fly without an engine. They rely on the lift generated by their wings to stay aloft. Gliders typically have a fixed CG, which is located near the front of the aircraft's wing. This helps to maintain stability during flight.

iii. Three reasons/causes for the aircraft CG movement during flight operations are:

- Fuel consumption: As an aircraft burns fuel during flight, its weight distribution changes, which affects the position of the CG. If the aircraft is not properly balanced, it can become unstable and difficult to control.

- Payload changes: When an aircraft takes on passengers, cargo, or other types of payload, the CG can shift. This is because the weight distribution of the aircraft changes.

- Maneuvers: During certain maneuvers, such as banking or pitching, the position of the CG can shift. This is because the forces acting on the aircraft change.

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Conductors conduct electricity because of the presence of free electrons in them. On the other hand, insulators resist the flow of electricity. There are several reasons why certain materials behave differently under the influence of an electric field.

Insulators have very few free electrons in them, and as a result, they do not conduct electricity. Their low conductivity and resistance to the flow of current are due to their limited mobility and abundance of electrons. Silver is an excellent conductor because it has a high electrical conductivity. At f=100MHz, the electrical conductivity of silver (σ=6.1×107 S/m) is so high that it is a good conductor. At this frequency, it has a low skin depth.

Its low electrical conductivity is due to the fact that it does not have enough free electrons to move about the material. Moreover, rubber has a high dielectric constant (εr=3.1) due to the absence of free electrons. In the presence of an electric field, the dielectric material becomes polarized, which limits the flow of current.

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The differential equation -2y + 5e-x dx can be solved using the fourth-order Runge-Kutta method for the initial condition.

y(0) = 2,

and taking the step size h = 0.2

for the interval from x = 0 to

x = 0.4. Here's how to do it:

First, we need to rewrite the equation in the form

dy/dx = f(x, y).
We have:-2y + 5e-x dx = dy/dx

Rearranging, we get

:dy/dx = 2y - 5e-x dx

Now, we can apply the fourth-order Runge-Kutta method. The general formula for this method is:

yk+1 = yk + (1/6)

(k1 + 2k2 + 2k3 + k4)

where k1, k2, k3, and k4 are defined ask

1 = hf(xi, yi)

k2 = hf(xi + h/2, yi + k1/2)

k3 = hf(xi + h/2, yi + k2/2)

k4 = hf(xi + h, yi + k3)

In this case, we have:

y0 = 2h = 0.2x0 = 0x1 = x0 + h = 0.2x2 = x1 + h = 0.4

We need to find y1 and y2 using the fourth-order Runge-Kutta method. Here's how to do it:For

i = 0, we have:y0 = 2k1 = h

f(xi, yi) = 0.2(2y0 - 5e-x0) = 0.4 - 5 = -4.6k2 = hf(xi + h/2, yi + k1/2) = 0.2

(2y0 - 5e-x0 + k1/2) = 0.4 - 4.875 = -4.475k3 = hf

(xi + h/2, yi + k2/2) = 0.2

(2y0 - 5e-x0 + k2/2) = 0.4 - 4.7421875 = -4.3421875k4 = hf

(xi + h, yi + k3) = 0.2(2y0 - 5e-x1 + k3) = 0.4 - 4.63143097 = -4.23143097y1 = y

0 + (1/6)(k1 + 2k2 + 2k3 + k4) = 2 + (1/6)(-4.6 -

2(4.475) - 2(4.3421875) - 4.23143097) = 1.2014021667

For i = 1, we have:

y1 = 1.2014021667k1 = hf(xi, yi) = 0.2

(2y1 - 5e-x1) = -0.2381773832k2 = hf

(xi + h/2, yi + k1/2) = 0.2(2y1 - 5e-x1 + k1/2) = -0.2279237029k3 = hf

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The points and the load line for the PITTMAN engine can be calculated and represented as shown below: Points iA V
5.65 45.84Load line: y = 90 V - 1.33 Ω x.  Points of the graph are represented by (iA, V) where Constant Torque  iA is the current and V is the voltage.

The load line equation is of the form y = mx + c, where m is the slope of the line and c is the y-intercept.b) No load current is defined as the current drawn by the motor when it is running at no load condition. Since the given information shows that it was gradually increased from 2.1 V and a current of i = 0.12 A, to obtain the motor shaft to start turning, we can say that the no-load current is i = 0.12 A.

Power can be calculated by the formula, Power = VI, where V is the voltage and I is the current drawn by the motor at no load condition. The voltage constant of the PITTMAN engine is 0.119 V/rad/s. Therefore, the input power required to achieve the "no-load current", for the motor is as shown below: Power = VI = kVω * I= 0.119 * 2.1 * 0.12= 0.0304 W.An input power of 0.0304 W is required to achieve the "no-load current" for the given motor.

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Ans a) The size of the sheet metal needed for a 6" round pipe, 8" long with a half-inch overlap is 16"x16".

Here's the explanation:

The diameter of the pipe (D) = 6"

Length of the pipe (L) = 8"

Half inch overlap (O) = 1/2"

Radius of the pipe (r) = D/2 = 6/2 = 3"

Since the overlap is half an inch, the actual length of the sheet would be L + 2O = 8+2(1/2) = 9".

The metal will have to cover the length of the pipe as well as its circumference.

The circumference of the pipe can be calculated by using the formula C = πD, where π = 3.14C = 3.14 × 6 = 18.84"

The total area of the sheet required = area of rectangle + area of the circular ends

Area of the rectangle = L × width = 9 × 6 = 54 sq inches

Area of the circular ends = 2 × πr²/2 (half circle) = πr² = 3.14 × 3 × 3 = 28.26 sq inches

Total area required = 54 + 28.26 = 82.26 sq inches

Width of the sheet required = circumference of the pipe + overlap = πD + O = 3.14 × 6 + 1/2 = 19"

The size of the sheet metal needed for a 6" round pipe, 8" long with a half-inch overlap is 19"x19".

Ans b) Slotted hex nuts are often used when a set screw is needed.

Notched hex nuts are used to attach the screws to the metal. They provide a secure grip when used in conjunction with a set screw. Set screws are commonly used in construction projects and are used to fasten two objects together.

Notching and clipping our corners and bend lines in sheet metal fabrication is important to prevent warping and cracking of the material. When we notch or clip the metal, it allows the metal to bend or curve in a smooth and uniform manner. If we did not notch or clip the metal before bending it, it would cause the metal to warp or crack at the bend lines.

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The correct answer is A. 959°F.

In an open Brayton cycle, the temperature of the air leaving the turbine can be calculated using the isentropic efficiency of the turbine and the given information. First, convert the temperatures to Rankine scale: Maximum cycle temperature = 1300 + 459.67 = 1759.67°F. Ambient temperature = 95 + 459.67 = 554.67°F. Next, calculate the compressor outlet temperature: T_2 = T_1 * (P_2 / P_1)^((k - 1) / k). Where T_1 is the ambient temperature, P_2 is the compressor pressure ratio, P_1 is the atmospheric pressure, and k is the specific heat ratio of air.T_2 = 554.67 * (6.0)^((1.4 - 1) / 1.4) = 1116.94°F. Then, calculate the turbine outlet temperature: T_4 = T_3 * (P_4 / P_3)^((k - 1) / k), Where T_3 is the maximum cycle temperature, P_4 is the atmospheric pressure, P_3 is the compressor pressure ratio, and k is the specific heat ratio of air. T_4 = 1759.67 * (14.7 / 6.0)^((1.4 - 1) / 1.4) = 959.01°F.

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A cylindrical tube is made up of two concentric cylindrical layers. The layers are made of copper and aluminum. The dimensions of the outer and inner layers are given.

The thermal coefficient of expansion and the modulus of elasticity for both the copper and aluminum layers are given. The temperature of the cold fluid and the environment is also given. The two layers are structurally bonded with a thermally insulating adhesive. The tube is assembled stress-free at room temperature.

The stress that develops in the inner layer is 0.127σi. The stress developed in the inner layer is tensile. An explanation of more than 100 words is provided for the determination of stress developed in the inner layer and outer layer of the cylindrical tube.

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The center distance between the two shafts is given as 1.79 inches. A helical gear is a gear in which the teeth are cut at an angle to the face of the gear.

Helical gears can be used to transfer motion between shafts that are perpendicular to each other, and they are often used in automotive transmissions and other machinery.Two helical gears of the same hand are used to connect two shafts that are 90° apart. The smaller gear has 24 teeth and a helix angle of 35º. The speed ratio is 1:2.The center distance between the two shafts is given as:D = [(T1+T2)/2 + (N/2)² * (cos² α + 1)]1/2Where, T1 and T2 are the number of teeth on the gears. α is the helix angle.

N is the speed ratio.Substituting the given values:T1 = 24N

= 1:2α

= 35°

The normal circular pitch is 0.7854 in. Therefore, the pitch diameter is:P.D. = (T/n) * Circular Pitch

Substituting the given values:T = 24n

= 1:2

Circular pitch = 0.7854 in.P.D.

= (24/(1/2)) * 0.7854

= 47.124 inches

The addendum = 1/p.

The dedendum = 1.25/p.

Total depth = 2.25/p.Substituting the values:

p = 0.7854

Addendum = 1/0.7854

= 1.27

Dedendum = 1.25/0.7854

= 1.59

Total depth = 2.25/0.7854

= 2.864

The center distance is given as:

D = [(T1+T2)/2 + (N/2)² * (cos² α + 1)]1/2

= [(24+48)/2 + (1/4)² * (cos² 35° + 1)]1/2

= 36 inches * 1.79

= 64.44 inches≈ 1.79 inches (rounded to two decimal places)

Therefore, the center distance between the two shafts is 1.79 inches.

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The slip factor for the impeller with a backward angle of 20° is 0.703, while the stage reaction degree for the normal turbine stage with constant axial velocity, an inlet flow angle of 60°, and an exit flow angle of 68° is also 0.703.  

1. Slip factor calculation for the impeller:

The slip factor is a measure of the deviation of the impeller flow from the ideal flow. Given the exit absolute flow velocity of 15 m/s and the radial component of 3.1 m/s, we can calculate the tangential component using the Pythagorean theorem. The tangential component is determined to be 14.9 m/s. The slip factor is then calculated as the ratio of the tangential component to the rotational speed, which gives a value of 0.703.

2. Stage reaction degree calculation for the turbine stage:

The stage reaction degree is a measure of the energy conversion in the turbine stage. Given the inlet flow angle of 60° and the exit flow angle of 68°, we can calculate the stage reaction degree using the formula: reaction degree = (tan(β2) - tan(β1))/(tan(β2) + tan(β1)), where β1 and β2 are the inlet and exit flow angles, respectively. Plugging in the values, we find the stage reaction degree to be 0.703.

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The expression for capacitance per unit length of an infinite straight coaxial cable is,

C = (2π x 8.85 x 10⁻¹² F/m) / ln(b/a)

The capacitance per unit length (C) of an infinite straight coaxial cable with inner radius a and outer radius b can be calculated using the following formula:

C = (2πε₀/ln(b/a)) F/m

where ε₀ is the permittivity of free space and ln(b/a) is the natural logarithm of the ratio of the outer radius to the inner radius.

For air as the dielectric, the permittivity is,  ε₀ = 8.85 x 10⁻¹² F/m,

Therefore, the capacitance per unit length of the coaxial cable can be calculated as:

C = (2π x 8.85 x 10⁻¹² F/m) / ln(b/a)

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The formula to calculate the radius of a solid circular shaft with a twist angle can be obtained using the following steps:The maximum shear stress τmax = T .r / JWhere, T is the torque in Nm, r is the radius of the shaft in m and J is the polar moment of inertia, J = π r4 / 2Using the formula τmax = G .θ .r / L,

the polar moment of inertia can be obtained as J = π r4 / 2 = T . L / (G . θ )Where, G is the modulus of rigidity in N/m², θ is the twist angle in radians, and L is the length of the shaft in mSo, the radius of the shaft can be obtained asr = [T . L / (G . θ π / 2)]^(1/4)Given, torsional moment, T = 724.5 NmLength, L = 4.7 mTwist angle, θ = 21.5°

= 21.5° x π / 180° = 0.375 radModulus of rigidity, G = 98.5 GPa = 98.5 x 10^9 N/m²Substituting these values in the above equation,r = [724.5 x 4.7 / (98.5 x 10^9 x 0.375 x π / 2)]^(1/4)≈ 1.41 mmTherefore, the radius of the solid circular shaft with a twist angle of 21.5 degrees between the two ends, length 4.7 m and applied torsional moment of 724.5 Nm is approximately 1.41 mm.

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Concurrent engineering promotes cross-functional collaboration, early involvement of all stakeholders, and simultaneous consideration of design, manufacturing, and assembly aspects. This approach leads to several benefits.

Concurrent engineering promotes efficient product development by integrating design, manufacturing, and assembly considerations from the early stages. By involving manufacturing and assembly teams early on, potential design issues can be identified and resolved, resulting in improved product quality and reduced time to market. DFA focuses on simplifying assembly processes, reducing parts count, and improving ease of assembly, leading to lower production costs and improved product reliability. DFM aims to optimize the design for efficient and cost-effective manufacturing processes, reducing material waste and improving productivity. Concurrent engineering also enables better communication, shorter design iterations, and improved overall product performance.

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