Second order linear differential equations

In summary, the first problem deals with a system exhibiting over damping, with the solution being x(t) = CE**-4T + DE**-t and the values of C and D being 1/5. The second problem also deals with a system in over damping, but with a cosine input function. The solution would involve finding the xh and steady-state solutions.
  • #1
CloudKel
2
0

Homework Statement


a) ẍ + 5ẋ + 4x = 0
x(0) = 0, ẋ(0)=1
What type of damping?

b) ẍ + x = cos(t)
x(0) = 0, ẋ(0)= 1
What type of motion?

The Attempt at a Solution


a) Let x = R Eᴿᵀ

R = -4
R = -1

x(t) = CE**-4T + DE**-t

C + D = 0
-4C - D = 1

C = 1/5
D = 1/5

And it is over damping

I think this is the right answer for a) but i have no idea how to do b)
 
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  • #2
CloudKel said:

Homework Statement


a) ẍ + 5ẋ + 4x = 0
x(0) = 0, ẋ(0)=1
What type of damping?

b) ẍ + x = cos(t)
x(0) = 0, ẋ(0)= 1
What type of motion?

The Attempt at a Solution


a) Let x = R Eᴿᵀ

R = -4
R = -1

x(t) = CE**-4T + DE**-t

C + D = 0
-4C - D = 1

C = 1/5
D = 1/5

And it is over damping

I think this is the right answer for a) but i have no idea how to do b)

a is correct, didn't check your values though.

You need to solve b) in the same way.

Set the LHS to zero and solve for xh

and your steady-state solution would be the PI for the right side.
 

Related to Second order linear differential equations

1. What is a second order linear differential equation?

A second order linear differential equation is a mathematical expression that involves a second derivative of an unknown function and can be written in the form y'' + p(x)y' + q(x)y = g(x), where p(x) and q(x) are functions of x and g(x) is a known function.

2. What is the general solution to a second order linear differential equation?

The general solution to a second order linear differential equation is a family of functions that satisfies the equation. It contains two arbitrary constants, as a second order equation requires two initial conditions to be fully determined.

3. How do you solve a second order linear differential equation?

To solve a second order linear differential equation, you can use various methods such as the method of undetermined coefficients, the method of variation of parameters, or the Laplace transform method. You can also use software or calculators to find the solution.

4. What are the applications of second order linear differential equations?

Second order linear differential equations are used in various fields of science and engineering, such as physics, chemistry, biology, economics, and engineering. They are particularly useful in modeling systems that involve acceleration, oscillations, or growth and decay phenomena.

5. What are the similarities and differences between first and second order linear differential equations?

Both first and second order linear differential equations involve derivatives of an unknown function, but a second order equation has a second derivative while a first order equation has a first derivative. Additionally, a second order equation requires two initial conditions to be solved, while a first order equation only requires one. The methods used to solve them are also different.

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