MAST20029 ENGINEERING MATHEMATICS SAMPLE MID SEMESTER TEST
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MAST20029 ENGINEERING MATHEMATICS SAMPLE
MID SEMESTER TEST
1. Consider the double integral
x(3) sinh(y2 ) dydx.
(a) Sketch the region of integration.
(b) By changing the order of integration, evaluate the double integral. [5 marks]
2. Determine the surface area of the part of the surface z = xy that lies inside the cylinder given by x2 + y2 = 1 . [5 marks]
3. Let F(x, y, X) = (sin y cos x)i + (sin x cos y)j + e2zk.
(a) Show that F is a conservative vector field.
(b) Find a scalar function ϕ such that F = ∇ϕ .
(c) Let C be the boundary of the square with vertices (0, 0), (1, 0), (1, 1), (0, 1), in the x-y plane. Determine the work done by F in moving a particle in an anticlockwise direction around C . [7 marks]
4. Consider the surface S of the region V formed by the portion of the cylinder x2 + y2 ≤ 4 which lies between the planes z = 1 and z = 4. let S be oriented with an outward unit normal.
Use Gauss’ (Divergence) Theorem and cylindrical coordinates to express the flux
of the vector field
F(x, y, z) = (x3 i + y3j + z3 k)
across the surface as a triple integral.
THERE IS NO NEED TO EVALUATE THE INTEGRAL. [6 marks]
5. Consider the following system of differential equations
= x + 2y, dt
with general solution
= −4x − 5y
dt
[y(x) ] = α1 [ 1 ] e t + α2 [ 2 ] e 3t
Sketch the phase portrait near the critical point at the origin. To sketch the phase portrait, determine:
. any special cases of the orbits,
. how the orbits behave as t → −∞ ,
. how the orbits behave as t → ∞ ,
. the slope of the orbits when x = 0,
. the slope of the orbits when y = 0.
In your sketch, show all the straight line orbits and at least four general orbits. [7 marks]
2023-01-29