TBR Physics; Periodic Motion and Waves

[shoehornlettuce]

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I just have a question regarding example 5.1b in TBR physics. I'm curious as to why answer choice B "The potential energy at consecutive maxima decreases while the kinetic energy at consecutive maxima remains constant" is not also correct. By "maxima" they are referring to maximum amplitude correct? If this is the case, potential energy is decreasing because of dampening effects. Kinetic energy should be zero shouldn't it? At maximum amplitude there is no movement i.e. all the energy is stored as potential so kinetic is constant in the sense that it is zero at each maxima. Am I reading into this too much? Any help would be appreciated. Thanks

 

[milski]

I just have a question regarding example 5.1b in TBR physics. I'm curious as to why answer choice B "The potential energy at consecutive maxima decreases while the kinetic energy at consecutive maxima remains constant" is not also correct. By "maxima" they are referring to maximum amplitude correct? If this is the case, potential energy is decreasing because of dampening effects. Kinetic energy should be zero shouldn't it? At maximum amplitude there is no movement i.e. all the energy is stored as potential so kinetic is constant in the sense that it is zero at each maxima. Am I reading into this too much? Any help would be appreciated. Thanks

What you are saying is correct - max PE at maximum displacement from equilibrium point and 0 KE at that point.

You'll have to post the rest of the question/answers for more detailed comments.

 

[MedPR]

I just have a question regarding example 5.1b in TBR physics. I'm curious as to why answer choice B "The potential energy at consecutive maxima decreases while the kinetic energy at consecutive maxima remains constant" is not also correct. By "maxima" they are referring to maximum amplitude correct? If this is the case, potential energy is decreasing because of dampening effects. Kinetic energy should be zero shouldn't it? At maximum amplitude there is no movement i.e. all the energy is stored as potential so kinetic is constant in the sense that it is zero at each maxima. Am I reading into this too much? Any help would be appreciated. Thanks

Yes. KE will always be 0 (is constant) at a maxima regardless of how small/big the amplitude is.

Edit: Oh, you said that answer is not correct.. I guess by "maxima" they mean maximum energy and not maximum amplitude.

 

[shoehornlettuce]

Thanks for the quick replies. The question asks "For a system that undergoes dampened harmonic oscillation, what observation is ture?". It says answer choice D is correct "The speed at consecutive maxima decreases while the period at consecutive maxima remains constant." This makes sense but I also thought B was correct. Not sure if I'm misinterpreting the question or if there is an error in the book. Either way, just wanted to make sure I wasn't misunderstanding the concept. Thanks again.

 

[milski]

Hm, it would be good to know which maxima are they talking about. If it's displacement maxima, D is wrong - the speed there does not decrease, it's always zero.

If they are talking about maximum speed, D would make sense but that's rather unusual way to phrase it.

 

[MT Headed]

I guess by "maxima" they mean maximum energy and not maximum amplitude.

That's how I read it. Comparing the potential energy maxima, and then separately (and at different times) comparing when the kinetic energy is at its maxima.

 

[shoehornlettuce]

That's how I read it. Comparing the potential energy maxima, and then separately (and at different times) comparing when the kinetic energy is at its maxima.

I see what your saying. I guess I just misread the question. I was interpreting it as the max displacement from equilibrium at which point potential energy would be greatest and kinetic energy would be zero. Thanks for the clarification.