Wales Uni - Math & Physics Exam: Diff. Equations (MA11210), June '08, Exams of Differential Equations

The university of wales, aberystwyth - institute of mathematics & physics exam for differential equations (ma11210) held in june 2008. The exam consists of multiple-choice questions related to the order, degree, and linearity of differential equations, as well as finding their general solutions. The document also includes problems on separating variables, using integrating factors, and solving specific differential equations.

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2012/2013

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PRIFYSGOL CYMRU / UNIVERSITY OF WALES
ABERYSTWYTH
INSTITUTE OF MATHEMATICS & PHYSICS
SEMESTER 2 EXAMINATIONS, JUNE 2008
MA11210 - Differential Equations
Time allowed – 2hours
Full marks will be given for complete answers to all questions in Section A and to
three questions in Section B. In Section B, credit will be given for the best three
answers.
Calculators must not be used in this examination.
pf3
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PRIFYSGOL CYMRU / UNIVERSITY OF WALES

ABERYSTWYTH

INSTITUTE OF MATHEMATICS & PHYSICS

SEMESTER 2 EXAMINATIONS, JUNE 2008

MA11210 - Differential Equations

Time allowed – 2hours

Full marks will be given for complete answers to all questions in Section A and to three questions in Section B. In Section B, credit will be given for the best three answers.

Calculators must not be used in this examination.

Section A

  1. Write down the order and degree of the following differential equations and state whether or not they are linear. [5]

a) 1

x

xy dx

dy x.

b) 2 2 1

2

  • cosy = dx

d y .

c) 2 1

2 2

2  +^ = 

  • y dx

dy dx

d y .

d) 2 1

2

2

2  + +^ = 

y dx

dy dx

y

d^.

e) 2 4

2 2 xe y x dx

y (^) x

  • = d .
  1. Find the general solution of the differential equation:

e cos x dx

dy (^) x = 2 −^2 +. [5]

  1. Find the general solution of the differential equation:

dx x ( x )

dy

, x > 0. [5]

  1. The differential equation: ( ) x y dx

dy 1 + x^3 =^2 is valid for x > 0. By separation of

variables, or otherwise, find the solution that satisfies y ( 1 ) = 2.

  1. Using an integrating factor, or otherwise, determine the solution of the following differential equation that satisfies y(0) = 1:

− 3 y = 0

dx

dy

. [5]

  1. Use an integrating factor to determine the solution of the following differential equation:

t

t te

t

x

dt

dx −

− = +. [5]

  1. a) A series circuit has a capacitor of C = 0.25 × 10 -6^ farad and an inductor of L = 1 henry. If the initial charge on the capacitor is q = 10-6^ coulomb and there is no initial current, find the charge q on the capacitor at any time t. [10] b) A series circuit has a capacitor of 10-5^ farad, a resistor of 3 × 102 ohms and an inductor of 0.2 henry. If the initial charge on the capacitor is 10-6^ coulomb and there is no initial current, find the charge q on the capacitor at any time t. [10]
  1. Show that the following non-linear equation:

( ) ( )

dy p x y q x yn

dx

  • = (^) , ( nR , n ≠ (^0) ),

may be transformed into a linear first-order equation for the new dependent variable

v , where v = y^1 −^ n. Obtain a general expression for the solution. [12]

Find the solution of the differential equation: 1

dy 4 y 2 e yx 2 , x

dx

for which y = 0 when x = 0. [8]