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Cavey wrote:

MaliA wrote:

Momentum isn't a function of time.

If I have one 1500kg body travelling at a steady speed of 70mph, and another 1500kg body that's accelerating very rapidly but whose instantaneous speed was also 70mph at the precise moment brakes were applied, which do you think will require the greater braking force?

John McDonnell

The car's got shit tons of momentum, sure - but I'm saying that a car that's just accelerated to 70 and a car that's been at 70 for the last five miles have identical momentum.

f does equal ma indeed, so the second you're no longer supplying engine power, the f is zero and a is also zero, no?

Cras wrote:

f does equal ma indeed, so the second you're no longer supplying engine power, the f is zero and a is also zero, no?

But that's the point. You were (microseconds before) applying (significantly boosted) engine power, so 'a' is still happening. Stop thinking in static speed terms.

Cras wrote:

Should it matter? Surely a set of brakes takes X distance to stop a car going at 40mph, regardless of how many bhp got it there? Or is the assumption that more bhp means you're just going to be going faster.

Well, with much more power, you're inevitably going to be presenting your brakes with faster rates of acceleration than otherwise would be the case, when they're applied (and therefore more likely to be applied more sharply than they would've hitherto been, so it's a bit of a double whammy, really). It's not about static, steady speeds motorway-style; the reality is a far more dynamic accelerative/decelerative picture.

Physics innit.

Jem wrote:

GazChap wrote:

I too, have just bought a car. To Jem's eternal astonishment.

Obviously the only thing I was astonished about was how long it took you.

You must be looking forward to your new 12.9 inch iPad Pro and one of those ace smart keyboard things and a swizzy iPad pen. Very kind of Gazchap to do that.

Findus Fop wrote:

Jem wrote:

GazChap wrote:

I too, have just bought a car. To Jem's eternal astonishment.

Obviously the only thing I was astonished about was how long it took you.

You must be looking forward to your new 12.9 inch iPad Pro and one of those ace smart keyboard things and a swizzy iPad pen. Very kind of Gazchap to do that.

I'm fairly sure that I said I wanted sex every day for the next 20 years if he gets a BMW but I think he's forgotten that....

Findus Fop wrote:

Jem wrote:

GazChap wrote:

I too, have just bought a car. To Jem's eternal astonishment.

Obviously the only thing I was astonished about was how long it took you.

You must be looking forward to your new 12.9 inch iPad Pro and one of those ace smart keyboard things and a swizzy iPad pen. Very kind of Gazchap to do that.

I'm fairly sure that I said I wanted sex every day for the next 20 years if he gets a BMW but I think he's forgotten that....

Jem wrote:

Findus Fop wrote:

Jem wrote:

GazChap wrote:

I too, have just bought a car. To Jem's eternal astonishment.

Obviously the only thing I was astonished about was how long it took you.

You must be looking forward to your new 12.9 inch iPad Pro and one of those ace smart keyboard things and a swizzy iPad pen. Very kind of Gazchap to do that.

I'm fairly sure that I said I wanted sex every day for the next 20 years if he gets a BMW but I think he's forgotten that....

How is that a deterrent?

Guys, guys. I ain't no physics teacher. If you don't believe me, why do you suppose that a 155mph limited BMW M3 has much better brakes than an equally 155mph speed limited BMW 330i or whatever? They both do the same top speed and they both weigh the same, so why bother? And why do people always say upgrade brakes with any remap such as this?

I've tried to give examples like the bullet etc. but I can't think of any other way to explain it so I give up, as I have homemade gnocchi waiting.

Cras wrote:

I get in trouble doing this, but assuming the acceleration is no longer being applied, surely the answer is that they require identical braking force?

Okay, consider a rifle bullet that weighs 10g that's been fired (the force is removed), say one hundreth of a second after it's been fired. It's travelling, say, at only 5mph, but it's accelerating like fuck.

Cavey wrote:

Surely bullets are slowing down as soon as they leave the barrel. How can something keep accelerating once the acceleration force is no longer being applied?

markg wrote:

Cavey wrote:

Surely bullets are slowing down as soon as they leave the barrel. How can something keep accelerating once the acceleration force is no longer being applied?

Interesting bullet fact that's pretty obvious but a not a lot of people think through - it you shoot a bullet from a gun in a straight line (ie, not upward) and drop a bullet from your hand when you pull the trigger, they'll both hit the ground at the same time.

Single handedly keeping the second hand car trade alive in the Isle of Man

MrChris wrote:

Single handedly keeping the second hand car trade alive in the Isle of Man

The car dealer(s) must have a nickname for Hearthly.

The Golden Goose?

Jem wrote:

Findus Fop wrote:

Jem wrote:

GazChap wrote:

I too, have just bought a car. To Jem's eternal astonishment.

Obviously the only thing I was astonished about was how long it took you.

You must be looking forward to your new 12.9 inch iPad Pro and one of those ace smart keyboard things and a swizzy iPad pen. Very kind of Gazchap to do that.

I'm fairly sure that I said I wanted sex every day for the next 20 years if he gets a BMW but I think he's forgotten that....

How is that a deterrent?

There are some electrical issues though. Like it won't lock consistently from the key fob. And the driver's side wing mirror won't fold. And the passenger's side seatbelt extender doesn't work. And there's an airbag error on the dash. And the driver's side headrest won't go up and down. Some slight vibration under braking too so could be a warped disc.

This is a stupid idea!

Lonewolves wrote:

While reading this, I have quite literally only just realised why you sent me that picture yesterday. I genuinely thought you were complaining about some other knobber parking in your space.

I'm a dick.

Lonewolves wrote:

A massive dick

I was young, I needed the money etc.

Is the Merc the biggest car you've owned? Looks like it's a fair bit bigger than a Type-R

Ooh, red bits on the seats

Amusing to me that it came from a BMW dealer at some point

Looks like a nice place to be inside - very different car to the Type-R though, why the change?

GazChap wrote:

Ooh, red bits on the seats

Amusing to me that it came from a BMW dealer at some point

Looks like a nice place to be inside - very different car to the Type-R though, why the change?

Wanted something a bit more grown up. The Civic was loud even when driving it sensibly.

I should be able to get £2.5k for the Civic so I'll use that £1k balance to get some over 50s life cover and a free Parker pen just for enquiring.

Author:	Cavey [ Tue Aug 08, 2017 19:09 ]
Post subject:	Re: Gas Guzzling Money Pits
ApplePieOfDestiny wrote: Cavey wrote: MaliA wrote: Momentum isn't a function of time. If I have one 1500kg body travelling at a steady speed of 70mph, and another 1500kg body that's accelerating very rapidly but whose instantaneous speed was also 70mph at the precise moment brakes were applied, which do you think will require the greater braking force? John McDonnell Harsh, but actually not a bad way to bring a speeding 1500kg accelerating mass to rest. I suppose it could happen with "ParkTronic" sensors and an oil-smoke haze...

Author:	Zardoz [ Tue Aug 08, 2017 19:13 ]
Post subject:	Re: Gas Guzzling Money Pits
I'd make sure your clutch and brakes are up to the job before a big increase like that.

Author:	Cras [ Tue Aug 08, 2017 19:14 ]
Post subject:	Re: Gas Guzzling Money Pits
f does equal ma indeed, so the second you're no longer supplying engine power, the f is zero and a is also zero, no?

Author:	MaliA [ Tue Aug 08, 2017 19:15 ]
Post subject:	Re: Gas Guzzling Money Pits
Momentum is mass times velocity

Author:	Cras [ Tue Aug 08, 2017 19:16 ]
Post subject:	Re: Gas Guzzling Money Pits
The car's got shit tons of momentum, sure - but I'm saying that a car that's just accelerated to 70 and a car that's been at 70 for the last five miles have identical momentum.

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Gas Guzzling Money Pits https://www.beexcellenttoeachother.com/forum/viewtopic.php?f=3&t=1635	Page 476 of 613

Author:	MaliA [ Tue Aug 08, 2017 19:17 ]
Post subject:	Re: Gas Guzzling Money Pits
Cras wrote: The car's got shit tons of momentum, sure - but I'm saying that a car that's just accelerated to 70 and a car that's been at 70 for the last five miles have identical momentum. Me, too.

Author:	Cavey [ Tue Aug 08, 2017 19:18 ]
Post subject:	Re: Gas Guzzling Money Pits
Cras wrote: f does equal ma indeed, so the second you're no longer supplying engine power, the f is zero and a is also zero, no? But that's the point. You were (microseconds before) applying (significantly boosted) engine power, so 'a' is still happening. Stop thinking in static speed terms.

Author:	MaliA [ Tue Aug 08, 2017 19:19 ]
Post subject:	Re: Gas Guzzling Money Pits
Cavey wrote: Cras wrote: f does equal ma indeed, so the second you're no longer supplying engine power, the f is zero and a is also zero, no? But that's the point. You were (microseconds before) applying (significantly boosted) engine power, so 'a' is still happening. Stop thinking in static speed terms. Acceleration and velocity are two different things

Author:	myp [ Tue Aug 08, 2017 19:20 ]
Post subject:	Re: Gas Guzzling Money Pits
Cavey wrote: Cras wrote: Should it matter? Surely a set of brakes takes X distance to stop a car going at 40mph, regardless of how many bhp got it there? Or is the assumption that more bhp means you're just going to be going faster. Well, with much more power, you're inevitably going to be presenting your brakes with faster rates of acceleration than otherwise would be the case, when they're applied (and therefore more likely to be applied more sharply than they would've hitherto been, so it's a bit of a double whammy, really). It's not about static, steady speeds motorway-style; the reality is a far more dynamic accelerative/decelerative picture. Physics innit. Let's not talk to Cras about physics

Author:	MaliA [ Tue Aug 08, 2017 19:20 ]
Post subject:	Re: Gas Guzzling Money Pits
I just tbought that.

Author:	MaliA [ Tue Aug 08, 2017 19:22 ]
Post subject:	Re: Gas Guzzling Money Pits
It doesn't matter how long the car took to get to 70mph, it'll require the same amount of force to stop it.

Author:	Cavey [ Tue Aug 08, 2017 19:23 ]
Post subject:	Re: Gas Guzzling Money Pits
Guys, guys. I ain't no physics teacher. If you don't believe me, why do you suppose that a 155mph limited BMW M3 has much better brakes than an equally 155mph speed limited BMW 330i or whatever? They both do the same top speed and they both weigh the same, so why bother? And why do people always say upgrade brakes with any remap such as this? I've tried to give examples like the bullet etc. but I can't think of any other way to explain it so I give up, as I have homemade gnocchi waiting.

Author:	Hearthly [ Tue Aug 08, 2017 19:39 ]
Post subject:	Re: Gas Guzzling Money Pits
I think it's fairly straightforward, as Cavey has already explained. If you're driving towards the limits of a car, including its brakes, the notion that '70mph is 70mph' really isn't the point, it's how quickly you're getting to 70 or 100 or 120 or 140 or whatever, and how frequently you need to slow down from those speeds. I honestly wouldn't want my S4 to be any more powerful than it already is, because as I found out over TT (when the mountain goes one-way, on what is already a derestricted road), once you've done a few sharp brakes down from 100mph+ and a lot of high speed braking in general, you'll be faced with some pretty significant brake fade, and that's a product of the car being able to get to 100mph in such a short period of time. Sure, my father-in-law's 1.4T Audi A1 will also get to 100mph eventually, but it'll do it far less often than my S4 will. Case in point is the attached image which is the charge down to Windy Corner (this is towards the end of the mountain run), I was already easing off a bit as I'd noticed brake fade over the last mile or two, but I was borderline alarmed by how much the stopping power of the brakes had been degraded as I slowed down to the 70-75mph or so you want to be at to get round this corner without too much screeching. So imagine punching another 80bhp into the equation, the car will be going even faster, more regularly, and the already strained brakes will be pushed even further, it's clearly not a sensible combination. (The Type-R on the other hand has 350mm grooved and drilled Brembos, I'm really quite looking forward to seeing how it holds up when TT comes around next year.) Attachment: windyo.JPG

Author:	MaliA [ Tue Aug 08, 2017 20:12 ]
Post subject:	Re: Gas Guzzling Money Pits
That's because putting the brakes on changes the energy of the car's movement into heat (and sound, on occasion). The brake disk cannot dissipate that heat as fast as it is being generated, when braking repeatedly. So, vented discs exist. A car at 70mph still has the same value of momentum at 70mph no matter how many times it has been at 70mph before or how long it took to get there.

Author:	krazywookie [ Tue Aug 08, 2017 20:15 ]
Post subject:	Re: Gas Guzzling Money Pits
Taking a step back here, bigger brakes are needed because yes, more power means people drive faster. The non physics is irrelevant, people be people.

Author:	Jem [ Tue Aug 08, 2017 20:27 ]
Post subject:	Re: Gas Guzzling Money Pits
Findus Fop wrote: Jem wrote: GazChap wrote: I too, have just bought a car. To Jem's eternal astonishment. Obviously the only thing I was astonished about was how long it took you. You must be looking forward to your new 12.9 inch iPad Pro and one of those ace smart keyboard things and a swizzy iPad pen. Very kind of Gazchap to do that. I'm fairly sure that I said I wanted sex every day for the next 20 years if he gets a BMW but I think he's forgotten that....

Author:	MaliA [ Tue Aug 08, 2017 20:29 ]
Post subject:	Re: Gas Guzzling Money Pits
Jem wrote: Findus Fop wrote: Jem wrote: GazChap wrote: I too, have just bought a car. To Jem's eternal astonishment. Obviously the only thing I was astonished about was how long it took you. You must be looking forward to your new 12.9 inch iPad Pro and one of those ace smart keyboard things and a swizzy iPad pen. Very kind of Gazchap to do that. I'm fairly sure that I said I wanted sex every day for the next 20 years if he gets a BMW but I think he's forgotten that.... Very good for dogging, those BMWs. Lots of room and lots of glass.

Author:	DavPaz [ Tue Aug 08, 2017 20:33 ]
Post subject:	Re: Gas Guzzling Money Pits
Jem wrote: Findus Fop wrote: Jem wrote: GazChap wrote: I too, have just bought a car. To Jem's eternal astonishment. Obviously the only thing I was astonished about was how long it took you. You must be looking forward to your new 12.9 inch iPad Pro and one of those ace smart keyboard things and a swizzy iPad pen. Very kind of Gazchap to do that. I'm fairly sure that I said I wanted sex every day for the next 20 years if he gets a BMW but I think he's forgotten that.... How is that a deterrent?

Author:	MaliA [ Tue Aug 08, 2017 20:37 ]
Post subject:	Re: Gas Guzzling Money Pits
DavPaz wrote: Jem wrote: Findus Fop wrote: Jem wrote: GazChap wrote: I too, have just bought a car. To Jem's eternal astonishment. Obviously the only thing I was astonished about was how long it took you. You must be looking forward to your new 12.9 inch iPad Pro and one of those ace smart keyboard things and a swizzy iPad pen. Very kind of Gazchap to do that. I'm fairly sure that I said I wanted sex every day for the next 20 years if he gets a BMW but I think he's forgotten that.... How is that a deterrent? (Types) (Deletes)

Author:	markg [ Tue Aug 08, 2017 20:43 ]
Post subject:	Re: Gas Guzzling Money Pits
Cavey wrote: Guys, guys. I ain't no physics teacher. If you don't believe me, why do you suppose that a 155mph limited BMW M3 has much better brakes than an equally 155mph speed limited BMW 330i or whatever? They both do the same top speed and they both weigh the same, so why bother? And why do people always say upgrade brakes with any remap such as this? I've tried to give examples like the bullet etc. but I can't think of any other way to explain it so I give up, as I have homemade gnocchi waiting. Surely bullets are slowing down as soon as they leave the barrel. How can something keep accelerating once the acceleration force is no longer being applied?

Author:	Sir Taxalot [ Tue Aug 08, 2017 23:24 ]
Post subject:	Re: Gas Guzzling Money Pits
Bigger expensive brakes look better behind big expensive alloy wheels than smaller cheaper brakes.

Author:	Mr Dave [ Tue Aug 08, 2017 23:43 ]
Post subject:	Re: Gas Guzzling Money Pits
Cavey wrote: Cras wrote: I get in trouble doing this, but assuming the acceleration is no longer being applied, surely the answer is that they require identical braking force? Okay, consider a rifle bullet that weighs 10g that's been fired (the force is removed), say one hundreth of a second after it's been fired. It's travelling, say, at only 5mph, but it's accelerating like fuck. Are you trying to win the Craster grenade physics awward or The Mr Chris Dynamo physics award?

Author:	Grim... [ Wed Aug 09, 2017 2:51 ]
Post subject:	Re: Gas Guzzling Money Pits
markg wrote: Cavey wrote: Guys, guys. I ain't no physics teacher. If you don't believe me, why do you suppose that a 155mph limited BMW M3 has much better brakes than an equally 155mph speed limited BMW 330i or whatever? They both do the same top speed and they both weigh the same, so why bother? And why do people always say upgrade brakes with any remap such as this? I've tried to give examples like the bullet etc. but I can't think of any other way to explain it so I give up, as I have homemade gnocchi waiting. Surely bullets are slowing down as soon as they leave the barrel. How can something keep accelerating once the acceleration force is no longer being applied? Interesting bullet fact that's pretty obvious but a not a lot of people think through - it you shoot a bullet from a gun in a straight line (ie, not upward) and drop a bullet from your hand when you pull the trigger, they'll both hit the ground at the same time.

Author:	Sir Taxalot [ Wed Aug 09, 2017 4:13 ]
Post subject:	Re: Gas Guzzling Money Pits
What if you fire the bullet out of a speeding car? Will it be different if the car is a family hatch or a powerful uber-wagon?

Author:	Sir Taxalot [ Wed Aug 09, 2017 4:15 ]
Post subject:	Re: Gas Guzzling Money Pits
What about if I'm doing a backflip from the roof of a speeding truck AND firing a gun at the same time. The car truck also has magnets in the wheels. And disco gear in the back.

Author:	TheVision [ Wed Aug 09, 2017 8:20 ]
Post subject:	Re: Gas Guzzling Money Pits
Don't forget it's being chased by Burtank!

Author:	Zardoz [ Wed Aug 09, 2017 9:00 ]
Post subject:	Re: Gas Guzzling Money Pits
We're all being chased by Burtank.

Author:	Mr Russell [ Wed Aug 09, 2017 9:23 ]
Post subject:	Re: Gas Guzzling Money Pits
Grim... wrote: markg wrote: Cavey wrote: Guys, guys. I ain't no physics teacher. If you don't believe me, why do you suppose that a 155mph limited BMW M3 has much better brakes than an equally 155mph speed limited BMW 330i or whatever? They both do the same top speed and they both weigh the same, so why bother? And why do people always say upgrade brakes with any remap such as this? I've tried to give examples like the bullet etc. but I can't think of any other way to explain it so I give up, as I have homemade gnocchi waiting. Surely bullets are slowing down as soon as they leave the barrel. How can something keep accelerating once the acceleration force is no longer being applied? Interesting bullet fact that's pretty obvious but a not a lot of people think through - it you shoot a bullet from a gun in a straight line (ie, not upward) and drop a bullet from your hand when you pull the trigger, they'll both hit the ground at the same time. Assuming a completely flat piece of ground, right? I imagine some of those more powerful guns would be able to fire far enough that you'd have to account for the curvature of the Earth.

Author:	Zardoz [ Wed Aug 09, 2017 9:28 ]
Post subject:	Re: Gas Guzzling Money Pits
Big brakes are heavier so they slow the car downier quickier.

Author:	Hearthly [ Wed Aug 09, 2017 10:13 ]
Post subject:	Re: Gas Guzzling Money Pits
Got a refund of £60 on the insurance which was unexpected, it only has a few months to run and I wouldn't have thought the Type-R was much cheaper (if at all) than the S4 to insure. The car will be ready anytime after 2pm on Friday, so I've put in for an early finish on that day so I can go vrooom vrooom vrooom and die horribly in a magnificent torque steer catastrophe.

Author:	Zardoz [ Wed Aug 09, 2017 10:51 ]
Post subject:	Re: Gas Guzzling Money Pits
Enjoy! Should have kept the old battery you bought for the S4 and pop it back in

Author:	MrChris [ Wed Aug 09, 2017 10:58 ]
Post subject:	Re: Gas Guzzling Money Pits
Single handedly keeping the second hand car trade alive in the Isle of Man

Author:	Findus Fop [ Wed Aug 09, 2017 11:10 ]
Post subject:	Re: Gas Guzzling Money Pits
MrChris wrote: Single handedly keeping the second hand car trade alive in the Isle of Man The car dealer(s) must have a nickname for Hearthly. The Golden Goose?

Author:	MrChris [ Wed Aug 09, 2017 11:12 ]
Post subject:	Re: Gas Guzzling Money Pits
Findus Fop wrote: MrChris wrote: Single handedly keeping the second hand car trade alive in the Isle of Man The car dealer(s) must have a nickname for Hearthly. The Golden Goose? I'm not sure they'd be that complimentary.