Author:
Short quiz for those who casually think about speed when they are driving or even when they see a vehicle speed by. Maybe they don't give it any thought.
Wolfjess' Speedway Demons brought to mind something I have contemplated since I was little. Only we are going to ramp up the speed from so long ago.
1: A vehicle is traveling at 200 mph. For simplicity's sake discount tire slippage on the surface.
2: How fast is the apex (top) of the tire traveling?
3. How fast is the bottom of the tire traveling where it fully contacts the surface?
Now I'm going to give a hint to the answers.
https://www.engineersedge.com/physics/speed_of_sound_13241.htm
Give it some thought before you read on down.
When I was growing up all tires had cord or thread in them. Slowly steel belted tires started making an appearance. There was a reason as tires were asked to run constantly at higher and higher speeds as turnpikes and interstates were built. The killer of corded tires was heat and centrifugal force. High speed sprints they usually held together. Long runs and they came apart. It was also the reason tubeless tires were introduced. The innertube constantly flexing against the inside of the tire built up excess heat.
Still haven't figured out the speed of the top of the tire on a car traveling at 200 mph? Remember we are ignoring friction loss on the surface. The top of the tire is traveling 400 mph relative to the surface the vehicle is traveling on. The bottom of the tire is traveling zero mph at full contact with the surface.
There are four tires traveling faster than the speed of sound on the vehicle traveling 200 mph. Which is part of the scream one hears as the vehicle races past and tires breaking the sound barrier.
There is so much physical science and mechanics going on every time one gets in a vehicle, starts it up, and begins driving..We live in an amazing and fascinating world if we just think about it. Shall I give a dissertation on the relationship of honey bees and their contribution to the foods we have or wouldn't have if it wasn't for the bees? Don't worry, I'm not. Had honey bees at one time. Thought I knew them. Taking a course at Michigan State University and I realize I knew nothing. They are even more fascinating than I imagined.
Hugs People, life is so precious, don't waste it.
Barb
Comments
Faster than the speed of sound?
The speed of sound in air at sea level and 68° F is 767 mph, or at 59° F, 761 mph. Either is greater than your 400 mph relative tire speed. I live near sea level and the highways I drive on are all near sea level.
This afternoon the temperature here was 69° F.
OOPS
DAB2640 is indeed right the speed of sound is 767 mph. The vehicle would need to be moving 400mph for the tires to break the speed of sound.
Thank you for the correction to the misplaced decimal in my math.
343.2 m/s (1,126 ft/s; 768 mph; 667.1 kn; 1,236 km/h
Hugs
Barb
Life is meant to be lived, not worn until it's worn out.
Oklahoma born and raised cowgirl
Units!
Did you confuse miles per hour with meters per second? (400 > 343)
-- Daphne Xu
You know me too well
Hugs Daphne
Barb
Oklahoma born and raised cowgirl
I know my students too well.
And this fell right into line.
-- Daphne Xu
Question 4
Question 4: How fast are the front and back of the tire moving? (The points halfway up.)
I PMed my answers to the two questions to her personally, to avoid giving the answer here. I think that answering this question 4 helps people respect what they might have called needless formalism.
This problem is related to the math in Still Another Dress Code.
-- Daphne Xu
The Answer
The wheel is spinning, and it's also moving to the right. To get the correct velocity of each point, we must add V = 200 mph rightward to all velocities.
-- Daphne Xu
A well known problem
for those involved with land speed record attempts.
If you want to travel faster than the speed of sound on land then the rim speed of the wheels is a huge problem. That will get beyond the speed of sound well before the vehicle itself. The stresses in the wheels are huge, really, really huge.
https://bloodhoundeducation.com/the-bloodhound-lsr-project/t...
That site has lots of 'I didn't know that' articles.
Samantha
I am a bit confused
Wouldn't the angular momentum be the same at top of the tire as the bottom of the tire? Then how can the bottom of the tire be traveling at zero mph?
Oh well. The inertial impact of your question has my head spinning I guess.
AuP
Angular Momentum
The angular momentum of a point particle is frame-dependent.
Place the origin of a stationary coordinate system at the height of the center of the wheel, then the angular momentum of the wheel is the same in that coordinate system, as about the center. But the angular momentum of individual points on the wheel is different.
Place your origin on the ground, the wheel has an additional angular momentum due to the straight-line motion of the wheel: the mass of the wheel * 200mph * the height of the center.
In either stationary frame, the bottom point has angular momentum zero.
-- Daphne Xu
It's a trick get an Axe!
Gotta love the amount of one liners in that old Bruce Campbell movie :)
trick question as the bottom of the tire is not moving in relation to the road and top is moving at twice the speed of the vehicle
We the willing, led by the unsure. Have been doing so much with so little for so long,
We are now qualified to do anything with nothing.
What?
What makes it a trick question? It's perfectly straightforward.
-- Daphne Xu
simple reasoning
At first glance most would think of the answer as the forward velocity of the tire which is in this case 200mph and that is a correct as the "whole" tire is traveling forward at that speed, although the actual question has nothing to do with the forward direction of the tire, but it's rotational speed at that velocity during a given moment in time. Which will always be zero where the tire is in contact with the road surface and twice the forward velocity at the top apex.
Sure there is mathematical formulas to prove the answer, but once you know the rules it is easy enough to come up with the answer.
Sort of like asking what the next number in the following sequence is, 2,3,5,7,11,13... If your quick with math, you immediately see this is a progression of prime numbers and know the next number in the sequence is of course 17. Therefore it's a trick question, the trick being you need to realize the sequence is of prime numbers.
We the willing, led by the unsure. Have been doing so much with so little for so long,
We are now qualified to do anything with nothing.
Right, it does seem like trick question
BUT, my dear friend Nuuan whom I have NOT heard a squeak out of for many months. Ignoring slippage, the average speed of the tire in relation to the vehicle and surface is indeed 200 mph, which I imagine many will lock onto. However our beautiful gal pal Daphne Xu not only possesses looks and a body figure but also an analytical mind figure. Girl is scary.
Hugs Nuuan
Oklahoma born and raised cowgirl
Sorry haven't been around much :(
Working for a badly understaffed IT department for a large school district during the pandemic has been been interesting (for lack of a more polite word)
Doc increased my nitroglycerine patches from 2mg/hr up to 4mg/hr and that in its self has taken me some months for my body to acclimatize.
On the bright side I have come up with a new project at home that has been providing some much needed stress relief. I bought a mid 90's full sized Ford Bronco back in January that now the weather has warmed I've been slowly restoring and upgrading. It's been a lot of fun working on it with the youngest one watching, asking questions and learning from me.
Last couple of nice weekends she has been helping me repair the modifications and crappy repairs previously done to the vehicles wiring by some less than knowledgeable shade-tree mechanic. While working on the wiring I've been upgrading the interior lighting and instrument panel to all LED lighting.
She has really gotten into helping and learning about this stuff, asking why was this done incorrectly and what is the correct way? How does this or that part work, why am I replacing it? Although I think her mom wasn't very impressed with me when she found her little girl sitting on the porch with my lock picks, locking and unlocking several padlocks I gave her to practice with after I had to explain how the ignition lock worked and why I replaced it.
And no, before anyone else asks, I will not be painting it white and putting a picture of OJ Simpson in the window :)
We the willing, led by the unsure. Have been doing so much with so little for so long,
We are now qualified to do anything with nothing.
But isn't life all about. . ..
. . .the real question about the variance in time of gravity's impact when Wild E. Coyote runs off a cliff?
And isn't the hum you hear at NASCAR the constant reactions of the fans to life's imponderables?
Why are they stealing Dr. Seuss' best novels from us? Hmmmmmmmmmmmmmmmmmm.
How do the Potatoheads reproduce? Hmmmmmmmmmmmmmmmmmmmmmmm.
Why do they keep talking about Matt Gaetz when Trump doesn't even remember ever meeting him -- at a party -- with lots of smokin' hot Ivanka-like teenagers who don't care if you grab them by the. . .. Hmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm.
Jill
Angela Rasch (Jill M I)
Of course this gets easy
Of course this all gets easier if you use an encabulator: https://www.youtube.com/watch?v=u4ILnWpi8XY
Your friend
Crash
But You Need a Degree . . . in Science
Now -- what do I do with my crate of encabulators I've stored in the basement, in case of emergency?
Jill
Angela Rasch (Jill M I)
Given the state of the world
Have you priced encabulators lately? The market has gone nuts. Apparently this whole "cyber gold rush" has blown the roof of anything that can turn electricity into heat. Encabulators are especially good at that task.
Your friend
Crash
The Blog isn't that far off subject
The girls have built this site for writers to post TG stories and for readers to find same. Most stories use a lot of fiction, others a little. The idea to post the tire speed hopefully to get people to understand or at least think about reality and life isn't as rigid as many believe. Everything around us including life is fluid. Some have questioned before they post a story if it's alright to describe a place, a person, an event other than what actually is as if every thing is cast in stone. Little do they know their concept of a place, a person in their story may be more close to the truth then the non fiction published about such.
Write what you feel, what gives you satisfaction, and tell your story from your perspective. Your hero got caught up in a chemical spill and changed to your heroine. Who is to say it can't happen? Free you mind and your gift for telling stories.
Hugs people
Barb
Life is a gift, don't waste it.
Oklahoma born and raised cowgirl
Speed(s)
Wouldn't the rotational speed be measured in RPM rather than MPH? The only time tangental velocity would be a issue would be if the tyre burst and a piece of rubber came flying towards you.
Actual Speed
No, the actual speed is wanted here. The rotational rate would be the speed divided by the radius.
Converting: 60 mph = 88 ft/s, so 200 mph = 293 ft/s. Suppose the wheel radius were 1 ft. The rotation rate would be (293 ft/s)/(1 ft) = 293 rad/s. Now convert it to rpm = rev/min: approximately 2800 rpm.
-- Daphne Xu
RPM vs MPH
For a given rotation (RPM), as you increase the size of the wheel on the shaft, the speed at the edge of the wheel increases.
Try it yourself with a length of string with a small weight on the end. Rotate it constantly and gradually let out the string.
What happens to the speed of the weight?
Hurry Up and Weight
Mortality ceases when the amount of weight in your life overwhelms the amount of action. It is that small weight at the end of our string that draws the final curtain.
Jill
Angela Rasch (Jill M I)