Differential equations (swinging door)

In summary, the conversation discusses a swing door with a damper and its characteristic polynomial. The general solution for x(0)=x_0 and v(0)=v_0 is given, as well as the initial conditions for x(0)=0.25. The conversation then moves on to discussing the initial velocity of the door and the solution for this scenario. Finally, the speaker shares that they have solved the problem on their own.
  • #1
Poetria
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Homework Statement


[/B]
There is a swing door with a damper. The characteristic polynomial (I have done it correctly) is:
0.5*r^2+1.5*r+0.625

General solution for x(0)=x_0 and v(0)=v_0 is (I have found it without a problem):

(1.25*x_0+v_0/2)*e^(-0.5*t)+((v_0+0.5*x_0)/(-2))*e^(-2.5*t)

Now the hell begins:
for x(0)=0.25
What can you say about the initial velocity of the door if, once the door is let go, it swings through the closed position and then swings back from the other side? (a numerical value and an appropriate inequality should be given)

The Attempt at a Solution


[/B]
Constants c_1 and c_2 given the initial conditions (x_0=0.25).

c_1+c_2=0.25
v_0=(0.25-c_2)*(-0.5)-c_2*(2.5)

The new solution:

(0.25-(v_0+0.125)/(-2))*e^(-0.5*t)+((v_0+0.125)/(-2))*e^(-2.5*t)

Well, now I am at my wits' end. I guess the velocity at the equilibrium position should be less than 0.

 
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  • #2
Hi, guys, I have solved it at last. No help necessary. Phew.
 
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What are differential equations and how are they related to the swinging door problem?

Differential equations are mathematical equations that describe how a quantity changes over time. In the swinging door problem, the position of the door changes over time due to various factors such as the force of gravity and the momentum of the door. These changes can be described using differential equations.

What is the general solution to the differential equation for the swinging door problem?

The general solution to the differential equation for the swinging door problem is y(t) = Ae^(kt) + Be^(-kt), where A and B are constants determined by initial conditions and k is a constant related to the properties of the door.

What is the significance of the constants A and B in the general solution?

The constants A and B in the general solution represent the initial conditions of the door, such as its initial position and velocity. These constants are crucial in solving specific scenarios of the swinging door problem.

How can differential equations be used to determine the behavior of the swinging door over time?

By solving the differential equation for the swinging door problem, we can determine the position and velocity of the door at any given time. This allows us to predict how the door will swing and how long it will take to come to a stop.

Are there any real-life applications of differential equations in the context of the swinging door problem?

Yes, differential equations are used in various fields, such as engineering and physics, to model and analyze the behavior of moving objects. In the case of the swinging door problem, differential equations can be used to design more efficient and stable doors for buildings or study the motion of pendulums.

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