Back and Forth Motion: Definition & Explanation

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In summary, the conversation discusses a type of motion where an object moves up and down, gaining more momentum at each cycle. The term for this type of motion is "simple harmonic motion" and can be modeled as a forced oscillator. Other terms mentioned include "resonance" and "undamped forced oscillation." The conversation also mentions a similar motion in a pendulum swing and its limitations. The conversation also touches upon the idea of this motion reaching a maximum level and not growing infinitely.
  • #1
viciam
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Hi guys,

I'm not a physicist or a mathematician but I have a question which will probably sound silly to you all

I need to know what that motion is called when you have an object and it moves up and down. But it gains more momentum every time it reaches the top so when it drops it goes down further and faster and when it reaches the maximum bottom it comes back up even faster and further and this cycle just keeps repeating. On every completion of up and down movement it goes further and further down and further and further up

In one word please tell me what this is called so I can google it. I inertia and reciprocating but this is not it. I know there's one word to describe this but I just can't remember it.

Thanks
 
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  • #2
In a periodic motion object moves back and foirth about its mean position.

The kind of motion you are describing can be more precisely called a 'Simple Harmonic Motion'.

Now you can google those two terms i described above
 
  • #3
Try "resonance".

But don't get sidetracked into crackpot websites about perpetual motion machines, "free energy", etc.
 
  • #4
Undamped forced oscillation:

http://www.nptel.iitm.ac.in/courses/Webcourse-contents/IIT-KANPUR/engg_mechanics/ui/Course_home_26.htm [Broken]
 
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  • #5
These all sound pretty complicated.

I thought it was as simple as a pendulum swing or something
 
  • #6
viciam said:
These all sound pretty complicated.

I thought it was as simple as a pendulum swing or something

You need to be putting energy in with each swing, to get bigger oscillatory motion. And there needs to be very little damping, so the energy being added in does not get dissipated by the damping.
 
  • #7
viciam said:
These all sound pretty complicated.

I thought it was as simple as a pendulum swing or something

Yes, you can do this with a swing. Either by pushing someone from outside or by yourself, flexing your legs at the right times. The amplitude increases at each cycle, up to a limit.
Can be modeled as a forced oscillator, as already mentioned.
But the math is not so simple, even for a "simple" pendulum, at large amplitudes.
 
  • #8
This is exactly what I'm trying to find out. You see how the waves become larger and larger as they go along? I typed in increasing oscillations in Google to get this image. http://www.nptel.iitm.ac.in/courses/Webcourse-contents/IIT-KANPUR/engg_mechanics/lecture26/26_1_clip_image059.gif [Broken]
 
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  • #10
A one-word description for this motion would be "impossible". Or "nonphysical". Or "imaginary". It does not exists in nature. The amplitude of oscillations may increase for a while, but then it will either reach some maximum level, or "bifurcate" into some other motion, which is a fancy way of saying "break into pieces".
 
  • #11
voko said:
A one-word description for this motion would be "impossible". Or "nonphysical". Or "imaginary". It does not exists in nature. The amplitude of oscillations may increase for a while, but then it will either reach some maximum level, or "bifurcate" into some other motion, which is a fancy way of saying "break into pieces".

One example of this oscillatory buildup which is very physical and non-destructive is the startup of a crystal oscillator. It starts with noise deviating the output of the oscillator amp a small amount, and the combination of positive & negative feedback builds up the oscillation slowly over many cycles until the oscillation limits itself at the nominal oscillator output amplitude.
 
  • #12
berkeman said:
One example of this oscillatory buildup which is very physical and non-destructive is the startup of a crystal oscillator. It starts with noise deviating the output of the oscillator amp a small amount, and the combination of positive & negative feedback builds up the oscillation slowly over many cycles until the oscillation limits itself at the nominal oscillator output amplitude.

So this reaches a maximum level, just like I said. It does not grow infinitely.
 
  • #13
voko said:
So this reaches a maximum level, just like I said. It does not grow infinitely.

Yes, absolutely. It just doesn't break into pieces like the Tacoma Narrows Bridge! :smile:
 

1. What is back and forth motion?

Back and forth motion is a type of movement where an object moves in one direction and then reverses its direction, repeating the same motion over and over again.

2. What is an example of back and forth motion?

An example of back and forth motion is a pendulum swinging back and forth.

3. How is back and forth motion different from other types of motion?

Back and forth motion is different from other types of motion because it involves a repetitive movement in one direction and then in the opposite direction, while other types of motion may involve movement in a single direction or in multiple directions at once.

4. What is the scientific explanation for back and forth motion?

Back and forth motion is caused by forces acting on an object, such as gravity or a force applied by a person or machine, that cause the object to move in one direction and then in the opposite direction.

5. What are some real-life applications of back and forth motion?

Back and forth motion is used in many everyday objects and machines, such as clocks, pendulum clocks, seesaws, and swings. It is also used in more complex systems, such as in engines and machinery, to convert rotational motion into back and forth motion.

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