Photo Contest - Kinetic Friction (10/12-10/18)

In summary, kinetic friction is the force that opposes the movement of an object when it is in motion. It is different from static friction, which occurs when an object is at rest. The amount of kinetic friction is affected by the type of surfaces in contact, the force pushing the surfaces together, and external factors like temperature or lubrication. Kinetic friction can be measured using a force sensor. Understanding kinetic friction is important in fields like engineering, physics, and material science, as it helps predict the behavior of moving objects and design more efficient machines and structures.
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ZapperZ
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Kinetic Friction

Kinetic friction is friction that occurs when something is moving and rubbing against another surface, creating such a friction. Your photo must clearly depicts a scenario in which such a thing is occurring. In includes cases where the friction is present but minimal, such as in ice skating.

Contest Rules:

1. Any digital photo or digitally-scanned photo relevant to the theme will be accepted within the contest period. In case there's a gray area, or you're not sure if the picture is suitable, check with me first.

2. Size limitations: Your photo is only limited to the file size limitation set by PhysicsForums. However, your may want to consider reducing the size of your photo if the file size exceeds 1 Mb. If your file is being hosted elsewhere, I will have to see how it is being displayed here, and I may ask you to resize and resubmit if it causes problems.

3. Upload your photos to any of the photo servers such as imageshack or photobucket. Then post it the relevant contest thread and link your picture using the img command. PM me if you do not know how. Alternatively, you may simply upload your image file to PF, and then have the full image displayed in your post.

4. Only ONE picture per member per contest. Once a picture is posted, it cannot be changed other than a total withdrawal by that member from that week's photo contest. Exceptions will be made for modification to comply with the rules, such as resizing.

5. At the end of the contest period, I will open a poll and every PF member can vote for the picture they like best.

6. Note that in case we have a large number of entries, I will do the polling in more than one thread. If that's the case, you can vote in each of the polling threads. The photos will be assigned in the polling threads in the order they were submitted.

7. The photo of the subject must be something that you took directly, not via in intermediary medium, and not taken by someone else. Unless otherwise noted, a photo of another photo, painting, print, etc. does not qualify.

8. You can use a picture only once. Once it is used in a contest, it cannot be reused in another contest.

9. Please post only pictures meant for submission in this thread. Photos not meant for submission must not be posted in the contest thread. Posting of more than one photos by a member may result in an automatic disqualification from the week's contest.

Zz.
 
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ZapperZ said:
Kinetic friction is friction that occurs when something is moving and rubbing against another surface, creating such a friction. Your photo must clearly depicts a scenario in which such a thing is occurring.
A flying aircraft or one that is about to land or take-off will count, considering the friction between the wings and air?
 
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Wrichik Basu said:
A flying aircraft or one that is about to land or take-off will count, considering the friction between the wings and air?

This is a great question, as I have lots of great pics showing fluid drag in various cases, but was unsure whether fluid drag would count as "kinetic friction" for the purposes of the contest. Due to the uncertainty, I went with a classic ice skating photo of my daughter.
 
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Wrichik Basu said:
A flying aircraft or one that is about to land or take-off will count, considering the friction between the wings and air?

No, air or wind drag does not count. We don't normally, at least in a General Physics course, consider those as kinetic friction. Air resistance varies with speed. Kinetic friction does not.

Zz.
 
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ZapperZ said:
No, air or wind drag does not count. We don't normally, at least in a General Physics course, consider those as kinetic friction. Air resistance varies with speed. Kinetic friction does not.

Zz.

For me, the trick is to (somehow) distinguish static and kinetic friction while using a static image. Interesting problem...
 
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Andy Resnick said:
For me, the trick is to (somehow) distinguish static and kinetic friction while using a static image. Interesting problem...

Yes, the photo must give a clear impression that the object is sliding, and not simply static. It isn't trivial.

Zz.
 
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Sometimes, just posing a question stimulates an answer:

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lekh2003 said:
A wheel rolling without slipping uses static friction, not kinetic friction. Is he braking? :oldwink:
 
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morrobay said:
lekh2003 said:

Unfortunately, I do not see the connection with kinetic friction in these two photos. Wind resistance, as has been stated, is not considered as kinetic friction, and neither is rolling friction, if the bike isn't skidding.

Zz.
 
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Well I certainly am not debating any physics PhD's here but in my Halliday-Resnick text: Forces acting between surfaces in relative motion are called forces of kinetic friction". Then since the oxygen and nitrogen molecules are in motion along the towel surface...
 
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morrobay said:
Well I certainly am not debating any physics PhD's here but in my Halliday-Resnick text: Forces acting between surfaces in relative motion are called forces of kinetic friction". Then since the oxygen and nitrogen molecules are in motion along the towel surface...

And air resistance is not such a force. Gasses have no "surfaces", so by the definition that you are using, air resistance and drag do not have kinetic friction.

zz.
 
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Final day to submit your photo for this contest.

Zz.
 
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Sorry guys :P, I guess I stretched it. It's alright.
 

1. What is kinetic friction?

Kinetic friction is the force that resists the motion of an object when it is in contact with a surface.

2. How does kinetic friction differ from static friction?

Kinetic friction occurs when an object is in motion, while static friction occurs when an object is at rest. Kinetic friction is usually less than static friction.

3. How can I measure kinetic friction?

Kinetic friction can be measured by using a force meter, also known as a spring scale, to determine the amount of force needed to keep an object in motion at a constant speed.

4. What factors affect the amount of kinetic friction?

The amount of kinetic friction is affected by the type of surface the object is in contact with, the roughness of the surface, and the weight and shape of the object.

5. How can I reduce kinetic friction?

Kinetic friction can be reduced by using lubricants, such as oil or grease, between the surfaces in contact. Smooth and polished surfaces also reduce the amount of kinetic friction.

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