P25752 – Engineering Mathematics and Numerical Analysis Academic Year 2022/23
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Academic Year 2022/23
P25752 – Engineering Mathematics and Numerical Analysis
Item 1 – Coursework
Question 1
The arc length of a segment of a parabola ABC of an ellipse with semi-minor axes a and b is given approximately by:
LABC = √b2 + 16a2 + ln ()
Write a universal, user-friendly code, test your programme and determine LABC if a = 11 cm and b = 9 cm.
[4 marks]
Question 2
The voltage difference Vab between points a and b in the Wheatstone bridge circuit is:
R1 R3 − R2 R4
(R1 + R2)(R3 + R4)
Write a universal, user-friendly code. Test you programme calculating the voltage difference when V = 14 volts, R1 = 120.6 ohms, R2 = 119.3 ohms, R3 = 121.2 ohms, and R4 = 118.8 ohms.
[5 marks]
Question 3
Newton's law of cooling gives the temperature T(t) of an object at time tin terms of T0, its temperature at t = 0, and TS , the temperature of the surroundings.
T(t) = TS + (T0 − TS )e−kt
A police officer arrives at a crime scene in a hotel room at 9:18PM, where he finds a dead body. He immediately measures the body's temperature and find it to be 26.4° C. Exactly one hour later he measures the temperature again, and find it to be 25.5° C. Determine the time of death, assuming that victim body temperature was normal (36.6° C) prior to death, and that the room temperature was constant at 20.5° C.
[10 marks]
Question 4
The volume of the parallelepiped shown can be calculated by TOB · (TOA × TAC ). Use the following steps in a script file to calculate the area. Define the vectors TOA, TOB , and TAC from inputted positions of points A, B, and C. Determine the volume by using MATLAB 's built-in functions dot and cross.
[4 marks]
Question 5
The position as a function of time (X (t),y(t)) of a projectile fired with a speed of v0 at an angle a is given by
X (t) = v0 cos a ⋅ t, y(t) = v0 sin a ⋅ t − gt2
where g = 9.81 m/sec2 . The polar coordinates of the projectile at time t are (T (t), e(t)), where
T (t) = √X 2 (t) + y2 (t), tan e(t) =
Write a universal, user-friendly code. Test case: v0 = 162 m/sec and a = 70° . Determine T(t) and e(t) for t = 1, 6, … , 31 sec.
[6 marks]
Question 6
The ideal gas equation states that P = , where P is the pressure, V is the volume, T is the
temperature, R = 0.08206 (L atm)/(mol K) is the gas constant, and n is the number of moles. Real gases, especially at high pressure, deviate from this behaviour. Their response can be modelled with the van der Waals equation
nRT n2 a
P = −
where a and b are material constants. Consider 1 mole (n = 1) of nitrogen gas at T = 300K. (For nitrogen gas a = 1.39 (L2 atm)/mol2, and b = 0.0391 L/mol.) Create a vector with values of Vs for 0. 1 ≤ V ≤ 1 L, using increments of 0.02 L. Using this vector calculate P twice for each value of V, once using the ideal gas equation and once with the van der Waals equation. Using the two sets of values for P,
calculate the percent of error () for each value of V . Finally, by using MATLAB's built-in
function max, determine the maximum error and the corresponding volume.
[4 marks]
Question 7
A food company manufactures five types of 8 oz Trail mix packages using different mixtures of peanuts, almonds, walnuts, raisins, and M&Ms. The mixtures have the following compositions:
|
Peanuts (oz) |
Almonds (oz) |
Walnuts (oz) |
Raisins (oz) |
M&Ms(oz) |
Mix 1 |
3 |
1 |
1 |
2 |
1 |
Mix 2 |
1 |
2 |
1 |
3 |
1 |
Mix 3 |
1 |
1 |
0 |
3 |
3 |
Mix 4 |
2 |
0 |
3 |
1 |
2 |
Mix 5 |
1 |
2 |
3 |
0 |
2 |
How many packages of each mix can be manufactured if 128 lb of peanuts, 118 lb of almonds, 112 lb of walnuts, 112 lb of raisins, and 104 lb of M&Ms are available? Write a system of linear equations and solve.
[5 marks]
Question 8
The electrical circuit shown consists of resistors and voltage sources. Determine i1, i2, i3, i4, and i5, using the mesh current method based on Kirchhoff's voltage law
V1 = 40 V, V2 = 30 V, V3 = 36 V, R1 = 16 Ω, R2 = 20 Ω, R3 = 10 Ω, R4 = 14 Ω, R5 = 8 Ω, R6 = 16 Ω, R7 = 10 Ω, R8 = 15 Ω, R9 = 6 Ω, R10 = 4 Ω .
[6 marks]
Question 9
A student has a summer job as a lifeguard at the beach. After spotting a swimmer in trouble, they try to deduce the path by which they can reach the swimmer in the shortest time. The path of shortest distance (path A) is obviously not the best since it maximizes the time spent swimming (they can run faster than they can swim). Path B minimizes the time spent swimming, but is probably not the best, since it is the longest (reasonable) path. Clearly the optimal path is somewhere in between paths A and B.
Consider an intermediate path C and determine the time required to reach the swimmer in terms of the running speed vTun = 3 m/sec, the swimming speed vswim = 1 m/sec, the distances L = 48 m, ds = 30 m, and dw = 42 m; and the lateral distance y at which the lifeguard enters the water. Create a vector y that ranges between path A and path B (y = 20, 21, 22, ... , 48 m) and compute a time t for each y . Use MATLAB built-in function min to find the minimum time, and the entry pointy for which it occurs. Determine the angles that correspond to the calculated value of y and investigate whether your result satisfies Snell's law of refraction:
sin p vTun
=
sin a vswim
Is there any other way to optimise the path?
[10 marks]
Question 10
In a typical tension test a dog bone shaped specimen is pulled in a machine. During the test, the force needed to pull the specimen and the length L of a gauge section are measured. This data is used for plotting a stress-strain diagram of the material. Two definitions, engineering and true, exist for stress
and strain. The engineering stress GC and strain cC are defined by GC = and cC = , where L0
and A0 are the initial gauge length and the initial cross-sectional area of the specimen, respectively.
The true stress Gt and strain ct are defined by Gt = and ct = ln .
The following are measurements of force and gauge length from a tension test with an aluminium specimen. The specimen has a round cross section with radius 6.4 mm (before the test). The initial gauge length is L0 = 25 mm. Use the data to calculate and generate the engineering and true stress- strain curves, both on the same plot. Label the axes and use a legend to identify the curves. Units: When the force is measured in newtons (N) and the area is calculated in m2, the unit of the stress is pascals (Pa).
F, N |
0 |
13.031 |
21.485 |
31.3963 |
34.727 |
37.119 |
37.960 |
39.550 |
40.758 |
L, mm |
25.400 |
25.474 |
25.515 |
25.575 |
25.615 |
25.693 |
25.752 |
25.978 |
26.419 |
F, N |
40.986 |
41.076 |
41.255 |
41.481 |
41.564 |
|
|||
L, mm |
26.502 |
26.600 |
26.728 |
27.130 |
27.441 |
[8 marks]
Question 11
A railroad bumper is designed to slow down a rapidly moving railroad car. After a 20,000 kg railroad car traveling at 20 m/sec engages the bumper, its displacement X (in meters) and velocity v (in m/sec) as a function of time t (in seconds) is given by:
X (t) = 4.219(e−1. 58t − e−6.32t) and v(t) = 26.67e−6.32t − 6.67e−1. 58t
Plot the displacement and the velocity as a function of time for 0 ≤ t ≤ 4 sec. Fit two plots at the top of the window and a plot of both with two vertical axes underneath them. All plots must be of the printing quality.
[8 marks]
Question 12
Aircraft A is flying east at 320 mi/hr, while aircraft B is flying south at 160 mi/hr. At 1:00 p.m. the aircraft are located as shown.
Obtain the expression for the distance D between the aircraft as a function of time. Plot D versus time until D reaches its minimum value. The plot must be of a printing quality. Use the roots function to compute the time when the aircraft are first within 30 mi of each other.
[6 marks]
Question 13
A two-dimensional state of stress at a point in a loaded material in the direction defined by the X − y coordinate system is defined by three components of stress G , Gyy and Ty . The stresses at the point in the direction defined by the X′ − y′ coordinate system are calculated by the stress transformation equations:
G − Gyy G + Gyy
Gy ′y ′ = G + Gyy − G ′ ′
G − Gyy
where e is the angle shown in the figure. Write a user-defined MATLAB function that determines the stresses G ′ ′ , Gy ′y ′ and T ′ y ′ given the stresses G , Gyy and Ty , and the angle e . For the function name and arguments, use ]S?Join[ =S?JassTJons )S‘ ?V(. The input argument S is a vector with the values of the three stress components G , Gyy and Ty and the input argument ?V is a scalar with the value of e . The output argument S?Join is a vector with the values of the three stress components G ′ ′ , Gy ′y ′ and T ′y ′ .
[7 marks]
Question 14
The ladder of a fire truck can be elevated (increase of angle p), rotated about the z axis (increase of angle), and extended (increase of T). Initially the ladder rests on the truck ( p = 0 , e = 0, and T = 8 m). Then the ladder is moved to a new position by raising the ladder at a rate of 5 deg/sec, rotating z at a rate of 8 deg/sec, and extending the ladder at a rate of 0.6 m/sec. Determine and plot the position of the tip of the ladder for 10 seconds.
[8 marks]
Question 15
The stresses fields near a crack tip of a linear elastic isotropic material for mode I loading are given by:
aXX = √T cos (1 − sin sin )
TXy = √2(K)几(I)T cos sin cos
For KI = 330 MPa-m0.5 produce contour plots of each stress in the same window. The domain is 0 ≤ e ≤ 90° and 0.01 ≤ T ≤ 5 mm. The plots must be of a printing quality.
[9 marks]
2022-10-21