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

  • Thread starter ZapperZ
  • Start date
  • #1
ZapperZ
Staff Emeritus
Science Advisor
Education Advisor
Insights Author
35,847
4,669
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.
 

Answers and Replies

  • #2
epenguin
Homework Helper
Gold Member
3,796
829
fullsizeoutput_28.jpeg
 
  • Like
Likes DrClaude, berkeman, BillTre and 1 other person
  • #3
morrobay
Gold Member
759
205
IMG-20191015-083950.jpg
 
  • #4
lekh2003
Gold Member
562
333
1571145802595.png
 
  • Like
Likes Rubidium_71 and fresh_42
  • #6
1,552
1,425
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?
 
  • #7
Dr. Courtney
Education Advisor
Insights Author
Gold Member
3,260
2,402
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.
 
  • #8
ZapperZ
Staff Emeritus
Science Advisor
Education Advisor
Insights Author
35,847
4,669
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.
 
  • #9
Andy Resnick
Science Advisor
Education Advisor
Insights Author
7,509
2,078
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....
 
  • #10
ZapperZ
Staff Emeritus
Science Advisor
Education Advisor
Insights Author
35,847
4,669
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.
 
  • #11
Andy Resnick
Science Advisor
Education Advisor
Insights Author
7,509
2,078
Sometimes, just posing a question stimulates an answer:

DSC_4569 copy.jpg
 
  • Like
Likes Rubidium_71, BillTre, WWGD and 1 other person
  • #12
247
206
marzena_kinetic_friction.JPG
 
  • Like
Likes morrobay, BillTre and Dr. Courtney
  • #15
morrobay
Gold Member
759
205
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...
 
  • #16
ZapperZ
Staff Emeritus
Science Advisor
Education Advisor
Insights Author
35,847
4,669
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.
 
  • #17
morrobay
Gold Member
759
205
Thai massage
IMG_20191018_104350 (1).jpg
 
Last edited by a moderator:
  • #18
ZapperZ
Staff Emeritus
Science Advisor
Education Advisor
Insights Author
35,847
4,669
Final day to submit your photo for this contest.

Zz.
 
  • #19
lekh2003
Gold Member
562
333
Sorry guys :P, I guess I stretched it. It's alright.
 

Related Threads on PF Photo Contest - Kinetic Friction (10/12-10/18)

Replies
7
Views
2K
Replies
13
Views
872
Replies
12
Views
979
Replies
9
Views
3K
Replies
5
Views
1K
Replies
4
Views
1K
Replies
20
Views
4K
Replies
13
Views
1K
Replies
8
Views
2K
Replies
7
Views
2K
Top