Differential Eqns Flashcards

(9 cards)

1
Q

What is the general solution of a 2nd order homogeneous differential equation with two distinct real roots?

A

Solution is of the form:
𝑦 = 𝐢₁𝑒^{π‘Ÿβ‚π‘₯} + 𝐢₂𝑒^{π‘Ÿβ‚‚π‘₯},
where π‘Ÿβ‚ and π‘Ÿβ‚‚ are the roots.

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2
Q

What is the general solution for a 2nd order differential equation with repeated roots?

A

Solution is of the form:
𝑦 = (𝐢₁ + 𝐢₂π‘₯)e^{π‘Ÿπ‘₯},
where π‘Ÿ is the repeated root.

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3
Q

What is the general solution for a 2nd order differential equation with complex roots?

A

Solution is of the form:
𝑦 = 𝐢₁e^{𝛼π‘₯}(cos(𝛽π‘₯) + 𝐢₂sin(𝛽π‘₯))
where 𝛼 is the real part and 𝛽 is the imaginary part of the roots.

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4
Q

how to solve non homogenous first order ODE

A

do complementary function which is solution to homogenous case, then add the particular integral solution

particular integral by guessing most generic form of the RHS then subing

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5
Q

How to solve coupled first order differential eqns?

A

Rearrange to get one 2nd order in one variable, solve for that then substitute into one of the originals to get the other

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6
Q

Derive the formula for damped harmonic motion

A

F =ma

ma=-kx -rv

.. .
mX + rx + kx = 0

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7
Q

Condition for light damping?

A

Complex roots to AE

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8
Q

Condition for critical damping? And special?

A

Repeated roots to AE, it is special because it comes to rest in fastest possible time

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9
Q

Condition for heavy damping?

A

Distinct roots to AE

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