+The Science Asylum Indeed! In the future I think I need to limit myself to a video gestation period of nine months... Thanks so much for previewing and suggesting improvements, Nick!!
Jesse Mason No problem. Glad I could help! A nine month gestation sounds good for you. You probably can't do much better than that given everything else.
Interesting video and the results seems to be quite accurate. It was very interesting to find that mass gets eliminated out of equation, and that you could get fairly accurate sliding friction coefficient by simply sliding piece of tire with scales. However, I think that sliding friction is influenced significantly by heat of the tire at the contact with the tarmac. I read in some sources that very high temperatures produced with severe sliding can cause tarmac to produce lubrication, I guess thats also the reason of skidmarks appear (and we didn't see them in video). I suppose that also depends on some tarmac properties as they seem to have different softening temperatures, as well as tire thermal properties. I'd guess that even though mass was eliminated from equation, it probably influences tire heating which influences kinetic friction. I suppose method from this video is accurate enough within city driving speeds, but I'd bet that with high speeds the error would go up a lot.
Great video but I do not understand how that lightweight chunk of tire produces the same friction coefficient as the compressed tires that carry the weight of the car. I would think the car produces lots more friction with locked wheels than a small piece of tire that can be dragged with 1 finger.
Hi Jet Pilot! Good observation. The friction DOES increase with mass, but it increases by the exact same amount as the inertia, which is why the vehicle will skid/slip the same distance along the road regardless of its mass.
I have a question if the skid in question happened with the right side tires on pavement and the left side tires on gravel, how would this change the calculation? Would I need to find the co efficient of the tire sliding on the gravel?
Why is there a difference between the calculated answer and the real velocity? Is it due to air resistance? Slight difference in the coefficient of kinetic friction? Is that how police use skid marks to get the approximate velocity of the vehicles? What if the skid marks are not straight, but curved, does it affect the results?
Hi Zero. (And Michael.) Sorry for the delay! The difference could be attributed to a number of measurement uncertainties - did you see how we eyeballed the force required to pull the piece of tire along the ground at constant speed? The needle was bouncing all over the place! And it's very different if it's curved. I have video footage and a solution prepared for curved skid marks (I shot it the same day) but have yet to shoot the solution and do the voiceover. It's on my (very long) list of videos I plan on doing in the future... Cheers from Detroit!
+Jesse Mason Also the kinetic friction coefficient isn't constant. It decreases as velocity increases. Also determining the kinetic friction coefficient experimentally is pretty tough as it requires you to move the object at constant velocity(also Newton's first law).
Why did you use the rear wheels as your reference rather than the front wheels. If the skid mark begins from the front wheels and the car stops referenced to the front wheels, the car's wheelbase doesn't matter. And in heavy braking 60%-70% of the braking is from the front wheels.
Hi Tom. The skid marks for front and rear are on top of each other so it's unclear which is which. So we take the length from beginning to end and subtract the wheelbase to get the length of each individual tire's skid. Also, we're idealizing the vehicle as a rigid body and not accounting for heavy braking... and it works pretty well! Cheers from Detroit!
Friction causes heat so the melted tar and oil in the road is the actual mark. Not rubber crayons. Plus the “minimum” speed equals the square root of 30*d*f. Happy learning!
This is the word of the Wikipedia (praise be to Wales): "Contrary to popular belief, skid marks are not caused by pieces of rubber from the tire being deposited on the road because friction heats up the tire. Skid marks are actually bituminous oils in the asphalt that are heated because of the friction of breaking or accelerating and rise to the surface, leaving dark marks. This is why the marks fade." Thanks for the comment, Livefire!
"You take care of your units and your units will take care of you." Do a dimensional analysis and you'll see that those units won't work out to be speed units, which tells you the equation is incorrect. The thorough work through of this problem though is more an exercise of Newton's second law as it applies to kinetic friction. "He's a good man. And thorough."
The skid becomes darker during the duration of braking. Near the beginning is a lighter part of a the skid. Do you only account for the darker part of the skid which is easier to see?
Simple! ||||| Plane speed = (Max speed x Altitude x Fraction of pilot's portfolio in Bitcoin) / (Max altitude x Pilot's age) |||| "There are old pilots and there are bold pilots, but there are no old bold pilots."
Your video style is awesome i love seeing how physics works "in real life". Its a very nice switch up from the normal boring textbooks
+Get Shrekt Thanks, GS - that means a lot to me!
I'm so excited this is finally finished! This has been a long time coming.
+The Science Asylum Indeed! In the future I think I need to limit myself to a video gestation period of nine months... Thanks so much for previewing and suggesting improvements, Nick!!
Jesse Mason
No problem. Glad I could help! A nine month gestation sounds good for you. You probably can't do much better than that given everything else.
nice.
Your videos are super helpful and captivating. Thanks!!!
Thanks for the compliment, Ronnie!
Interesting video and the results seems to be quite accurate. It was very interesting to find that mass gets eliminated out of equation, and that you could get fairly accurate sliding friction coefficient by simply sliding piece of tire with scales. However, I think that sliding friction is influenced significantly by heat of the tire at the contact with the tarmac. I read in some sources that very high temperatures produced with severe sliding can cause tarmac to produce lubrication, I guess thats also the reason of skidmarks appear (and we didn't see them in video). I suppose that also depends on some tarmac properties as they seem to have different softening temperatures, as well as tire thermal properties. I'd guess that even though mass was eliminated from equation, it probably influences tire heating which influences kinetic friction.
I suppose method from this video is accurate enough within city driving speeds, but I'd bet that with high speeds the error would go up a lot.
Men you just saved my life🔥🙏🏼
Very nicely done.
Hello sir... You Explain so accurately and in a very easy way so that students can understand complete.... You are practically great. 👍👍👍👍👍👍
Great video. Well done!
Hello from Turkey :)How amazing video
Really amazing stuff wish I studied physics or engineering on a related field be cool to know these things
Did he just say “meow” @9:50 ?! Haha
Great video but I do not understand how that lightweight chunk of tire produces the same friction coefficient as the compressed tires that carry the weight of the car. I would think the car produces lots more friction with locked wheels than a small piece of tire that can be dragged with 1 finger.
Hi Jet Pilot! Good observation. The friction DOES increase with mass, but it increases by the exact same amount as the inertia, which is why the vehicle will skid/slip the same distance along the road regardless of its mass.
I have a question if the skid in question happened with the right side tires on pavement and the left side tires on gravel, how would this change the calculation? Would I need to find the co efficient of the tire sliding on the gravel?
Why is there a difference between the calculated answer and the real velocity? Is it due to air resistance? Slight difference in the coefficient of kinetic friction?
Is that how police use skid marks to get the approximate velocity of the vehicles? What if the skid marks are not straight, but curved, does it affect the results?
he dint reply lol .
hope he does soon.
Hi Zero. (And Michael.) Sorry for the delay! The difference could be attributed to a number of measurement uncertainties - did you see how we eyeballed the force required to pull the piece of tire along the ground at constant speed? The needle was bouncing all over the place! And it's very different if it's curved. I have video footage and a solution prepared for curved skid marks (I shot it the same day) but have yet to shoot the solution and do the voiceover. It's on my (very long) list of videos I plan on doing in the future... Cheers from Detroit!
+Jesse Mason Also the kinetic friction coefficient isn't constant. It decreases as velocity increases. Also determining the kinetic friction coefficient experimentally is pretty tough as it requires you to move the object at constant velocity(also Newton's first law).
Why did you use the rear wheels as your reference rather than the front wheels. If the skid mark begins from the front wheels and the car stops referenced to the front wheels, the car's wheelbase doesn't matter. And in heavy braking 60%-70% of the braking is from the front wheels.
Hi Tom. The skid marks for front and rear are on top of each other so it's unclear which is which. So we take the length from beginning to end and subtract the wheelbase to get the length of each individual tire's skid. Also, we're idealizing the vehicle as a rigid body and not accounting for heavy braking... and it works pretty well! Cheers from Detroit!
great video
really well done!
Thanks, JM.
where does Time Independent Equation, at 2:50, comes from?
Mihai Frunza kinematic equations
Friction causes heat so the melted tar and oil in the road is the actual mark. Not rubber crayons. Plus the “minimum” speed equals the square root of 30*d*f. Happy learning!
This is the word of the Wikipedia (praise be to Wales): "Contrary to popular belief, skid marks are not caused by pieces of rubber from the tire being deposited on the road because friction heats up the tire. Skid marks are actually bituminous oils in the asphalt that are heated because of the friction of breaking or accelerating and rise to the surface, leaving dark marks. This is why the marks fade." Thanks for the comment, Livefire!
Why not just Speed = 30 • Distance • Friction. Friction most of the time being 0.7 or 0.8
And square root the answer of that equation to get your speed
"You take care of your units and your units will take care of you." Do a dimensional analysis and you'll see that those units won't work out to be speed units, which tells you the equation is incorrect. The thorough work through of this problem though is more an exercise of Newton's second law as it applies to kinetic friction. "He's a good man. And thorough."
Awesome!
How did you determine the beginning and end of the skid? Besides the obvious dark marks of course.
Just by looking at the tyre marks.
The skid becomes darker during the duration of braking. Near the beginning is a lighter part of a the skid. Do you only account for the darker part of the skid which is easier to see?
Muito bom!!!
Awesome
Thanks, Dax!
Nice video.... Keep it
+Tell me Why Thanks, TMW! I'm very proud of this one.
Can't we use energy to solve this?
1/2v^2-ug(length of skid marks)=0
I knew there'd be a Back to The Future reference! 😂
Great Scot!
Must be quite the pool of Kyles around here
Can u do a video on heat please
Your wish has been granted. =)
no si units?
Converted it to MPH at the end because... 'merica.
It takes guts to do physics problems in sharpie.
Or multiple takes. ;) Cheers, Rusty!
They can only do this because they know the car weight and wheel diameter.
it was ocm
And yep watch my video as well
Computation assumed level road. Looks like it slopes down.
Hey Mr. K! Yes, I assumed a level road. The stretch I drove (after the first twenty feet) was fairly level.
Where can I hire a specialist to reconstruct an accident. I have skid Mark's pictures
I avoid skid marks at all costs
LOL
Now calculate the speed of an aeroplane if the piolets age is 63.
Yes.
Simple! ||||| Plane speed = (Max speed x Altitude x Fraction of pilot's portfolio in Bitcoin) / (Max altitude x Pilot's age) |||| "There are old pilots and there are bold pilots, but there are no old bold pilots."
I’m not dating your mom Mexico
Why can you not us feet? I am done
Michael Freeling because it's an inferior unit but it's not hard to convert
Because measuring in feet and span is too primitive for modern physics.
I try to wash my underwear before doing physics in them.