Mass Spring System: Find Natural Frequencies & Mode Shapes

In summary, for the case where m1=m2=m, the expressions for the natural frequencies and mode shapes can be obtained by doing a free body analysis and writing force/acceleration equations for each of the two masses. Considering mass m1, if it is displaced vertically downward by an amount x1, the forces in the springs, net vertical force, displacement relative to ground, and acceleration can be determined. This leads to a differential equation that can help solve the problem.
  • #1
acpower89
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Homework Statement


Obtain the expressions for the natural frequencies and mode shapes for the case where m1=m2=m.

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Homework Equations




The Attempt at a Solution



I apologise for not making an attempt, this is just unlike anything I've seen.

I'd appreciate if anyone could demystify this problem.
 
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  • #2
Do the usual free body analysis and write the force/acceleration equations for each of the two masses.
 
  • #3
Consider mass m1. If at some time t it is displaced vertically downward wrt m2 by an amount x1, what are the forces in the springs? What is ythe net vertical force on it? What is its displacement relative to the ground? What is its acceleration? What differential equation does that give you?
 

What is a mass spring system?

A mass spring system is a physical system consisting of a mass attached to a spring. The mass is free to move back and forth along a fixed axis, and the spring provides a restoring force that causes the mass to oscillate around its equilibrium position.

What are natural frequencies in a mass spring system?

Natural frequencies are the frequencies at which a mass spring system will oscillate when disturbed from its equilibrium position. These frequencies are determined by the properties of the mass (such as its mass and stiffness) and the spring (such as its spring constant).

How do you find natural frequencies in a mass spring system?

To find the natural frequencies in a mass spring system, you can use the equation:
f = (1/2π) * √(k/m)
where f is the frequency, k is the spring constant, and m is the mass. You can also use numerical methods or simulation software to calculate the natural frequencies.

What are mode shapes in a mass spring system?

Mode shapes are the shapes taken by a mass spring system when it oscillates at a particular natural frequency. They describe the displacement of the mass from its equilibrium position at different points in time.

How do you find mode shapes in a mass spring system?

To find the mode shapes in a mass spring system, you can use the equation:
x(t) = A * sin(2πft + φ)
where x(t) is the displacement of the mass, A is the amplitude, f is the natural frequency, and φ is the phase angle. You can also use numerical methods or simulation software to calculate the mode shapes.

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