Undamped Harmonic Oscillator Problem

In summary: The problem is simply asking for the condition that makes the amplitude solution for a single undamped oscillator independent of time.BvU is right, it is an energy conservation question. The amplitude is determined by the initial conditions, which can be expressed in terms of position and velocity. The answer given is correct, but it is in terms of the maximum acceleration and not the initial conditions. You can express the maximum acceleration in terms of the initial conditions, and then equate it to the given expression to solve for the initial conditions.
  • #1
Potatochip911
318
3

Homework Statement


Find the initial conditions for 2 interchangeable harmonic oscillators (undamped) so that they have the same amplitude of oscillation.

Homework Equations


x(t)=Xm*cos(wt+ϕ)

The Attempt at a Solution


The amplitude of the function is given by Xm so I would have thought that just having the same value for Xm would be the correct answer however I am obviously overlooking something since the answer is w2*x02+v02

w2*x02 appears to be the maximum acceleration of the function however I am at a complete loss as to how where they got v02
Also it's possible that for X0 they are referring to Xm, my university randomly changes notation from time to time for some reason.
 
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  • #2
Confusing, isn't it ?
For the harmonic oscillator you have a 2nd order differential equation, so there are two initial conditions. You can guess which two quantities need to be given an initial value. What is asked of you in this exercise is that you fill in two symols, e.g. v0 and x0 and find out what the resulting amplitude of the oscillation is in terms of those two. That expression is the relationship you are looking for: if that expression yields the same value, then the amplitude comes out the same too.

You answer is correct, but you have to express it in the initial conditions.

Your university is not wrong this time :wink:
 
  • #3
BvU said:
Confusing, isn't it ?
For the harmonic oscillator you have a 2nd order differential equation, so there are two initial conditions. You can guess which two quantities need to be given an initial value. What is asked of you in this exercise is that you fill in two symols, e.g. v0 and x0 and find out what the resulting amplitude of the oscillation is in terms of those two. That expression is the relationship you are looking for: if that expression yields the same value, then the amplitude comes out the same too.

You answer is correct, but you have to express it in the initial conditions.

Your university is not wrong this time
Sorry I'm still quite lost as to how to get the correct answer. After looking through some resources it appears as though the differential equation is d^2(x)/dt^2+w2*x=0 although I can't see what to do with it
 
  • #4
Potatochip911 said:
Sorry I'm still quite lost as to how to get the correct answer. After looking through some resources it appears as though the differential equation is d^2(x)/dt^2+w2*x=0 although I can't see what to do with it
Sorry for double post but I can't seem to edit my last post anymore. It appears as though this is actually a conservation of energy question. I am still getting the wrong answer after using the formula (1/2)*k*xo2+(1/2)*mv02=(1/2)*kxm2
After I solve this for xm I obtain x02+vo2/w2=xm2 which is still the wrong answer.
Edit: I just realized in my second last step before dividing both sides by w2 I have the answer, is it because they mention that the two oscillators are identical and that's why the value for w does't matter?
 
  • #5
"Identical oscillators" means they have the same ##\omega##.
 
  • #6
Potatochip911 said:

Homework Statement


Find the initial conditions for 2 interchangeable harmonic oscillators (undamped) so that they have the same amplitude of oscillation.
w2*x02 appears to be the maximum acceleration of the function
That can't be acceleration; the units are wrong.
The answer given to you makes no sense: initial conditions are dx/dt(0+) and d2x/dt2(0+), not a quantity with dimension L2T-2.
I think BvU has the intended interpretation of this confused problem statement right.
If so, the question should have been worded as follows: "what function (combination) of x(0) and v(0) must be constant for an undamped harmonic oscillator to exhibit the same amplitude of oscillation?"
In other words there was never a need to mention two oscillators at all.
 

Related to Undamped Harmonic Oscillator Problem

1. What is an undamped harmonic oscillator?

An undamped harmonic oscillator is a physical system that exhibits periodic motion, where the restoring force is proportional to the displacement from the equilibrium position. This type of oscillator does not experience any external damping forces, meaning it will continue to oscillate indefinitely with the same amplitude and frequency.

2. What is the equation of motion for an undamped harmonic oscillator?

The equation of motion for an undamped harmonic oscillator is given by x(t) = A cos(ωt + φ), where x(t) is the displacement from the equilibrium position at time t, A is the amplitude, ω is the angular frequency, and φ is the phase angle.

3. How does the mass and spring constant affect the motion of an undamped harmonic oscillator?

The mass and spring constant both play a role in determining the frequency and amplitude of the oscillations of an undamped harmonic oscillator. A larger mass will result in a lower frequency and a smaller amplitude, while a larger spring constant will result in a higher frequency and a larger amplitude.

4. How is energy conserved in an undamped harmonic oscillator?

Energy is conserved in an undamped harmonic oscillator because there is no external damping force acting on the system. The energy of the oscillator is constantly exchanged between kinetic energy (motion) and potential energy (stored in the spring), resulting in a constant total energy.

5. How is the period of an undamped harmonic oscillator related to its frequency?

The period of an undamped harmonic oscillator is the time it takes for one complete oscillation, while the frequency is the number of oscillations per unit time. These two quantities are inversely related, meaning that as the frequency increases, the period decreases and vice versa. This relationship is described by the equation T = 2π/ω, where T is the period and ω is the angular frequency.

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