XPost: uk.politics.misc, alt.sci.physics, sci.physics

Automotive brakes: these people obviously get cars to stop. So is the
heating proportional to velocity or velocity squared?

Say a 2000kg car at 120mph (moderately high performance, not
exceptional, about limit of normal cars)
or 30mph.

30mph - 13.4m/s
120mph - 53.6m/s

at 30mph - kinetic energy is 0.5*2000*13.4*13.4 = 179,560 J
at 120mph - kinetic energy is 0.5*2000*53.6*53.6 = 2,872,960J

Say 0.9G braking - 9m/s^2
0=54 +9*t^2

t= sqrt(54/9)
t= sqrt (6)
t = 2.44s, round up to 2.5

2,872,960 /4 = 718,240 , bit more at the front, say 750,000J

over 2.5 seconds, lots of watts. 3,600,000J = in 1 hour is 1kW

One second have 300,000J, which is a lot of watts and power for a
regular auto.

Stopping power = 300kw on one wheel, seems a lot to put brake pads say 200mmx100mm *2, even for a short time. Bearings, axle etc.

Electric car owners will have the luxury of knowing exactly how much
energy an acceleration cycle takes, and can compare and contrast.

The car people say that acceleration gets slower because of air
resistance as you get faster, not the extra kinetic energy needed,
because the square nature of the formula.

So, my expectancy is that if kinetic energy, and so gravity and a shed
more besides are wrong (E=0.5mv^2), physics across the planet will stop
being funded, since taxpayers don't fund kooks, and it is human nature
to throw the baby out with the bathwater. I'd give it 6 months.

Optics etc, I have no problem with, I was in about the first lab in the
world to have a room temperature thermal camera, and now I've bought one online. On another personal note, I've worked for UK, American, French companies, done an online course with Russians in Russia, and worked
more recently with people from the PRC. So all 5 should have a file.
They have permission to reuse my post on the three recent threads about
kinetic energy in whatever context (UN?), if they want a chin wag.

Saying kinetic energy is a computational convenience is OK to me, if the
exact same convenience is applied to free falling objects in a vacuum,
but where does all the energy from mgh lifting things up go to?

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XPost: uk.politics.misc, alt.sci.physics, sci.physics

On 23 13, Dave wrote:

Electric car owners will have the luxury of knowing exactly how much
energy an acceleration cycle takes, and can compare and contrast.

To test this you can have an electric car very close behind a large
truck to reduce air resistance as much as possible. Really need a
private road for safety.

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XPost: uk.politics.misc, alt.sci.physics, sci.physics

On 23 13, Dave wrote:

Automotive brakes: these people obviously get cars to stop. So is the
heating proportional to velocity or velocity squared?

Say a 2000kg car at 120mph (moderately high performance, not
exceptional, about limit of normal cars)
or 30mph.

30mph - 13.4m/s
120mph - 53.6m/s

at 30mph - kinetic energy is 0.5*2000*13.4*13.4 = 179,560 J
at 120mph - kinetic energy is 0.5*2000*53.6*53.6 = 2,872,960J

Say 0.9G braking - 9m/s^2
0=54 +9*t^2

t= sqrt(54/9)
t= sqrt (6)
t =  2.44s, round up to 2.5

2,872,960 /4 = 718,240 , bit more at the front, say 750,000J

over 2.5 seconds, lots of watts. 3,600,000J = in 1 hour is 1kW

Wrong there, sorry, there is no square root. Six seconds of hard braking.

One second have 300,000J, which is a lot of watts and power for a
regular auto.

Stopping power = 300kw on one wheel, seems a lot to put brake pads say 200mmx100mm *2, even for a short time.  Bearings, axle etc.

answer is (300*6)/2.5 = 125kW, still a lot for normal cars on one wheel,
should survive.

A nice example of how easy it is to fool yourself to get the answer you
expect. This braking is absolutely fine from total energy into the axle. Heating more of an issue? One time I checked my disks and there was a
dull red glow. They can take a lot.

Electric car owners will have the luxury of knowing exactly how much
energy an acceleration cycle takes, and can compare and contrast.

The car people say that acceleration gets slower because of air
resistance as you get faster, not the extra kinetic energy needed,
because the square nature of the formula.

So, my expectancy is that if kinetic energy, and so gravity and a shed
more besides are wrong (E=0.5mv^2), physics across the planet will stop
being funded, since taxpayers don't fund kooks, and it is human nature
to throw the baby out with the bathwater. I'd give it 6 months.

Optics etc, I have no problem with, I was in about the first lab in the
world to have a room temperature thermal camera, and now I've bought one online. On another personal note, I've worked for UK, American, French companies, done an online course with Russians in Russia, and worked
more recently with people from the PRC. So all 5 should have a file.
They have permission to reuse my post on the three recent threads about kinetic energy in whatever context (UN?), if they want a chin wag.

Saying kinetic energy is a computational convenience is OK to me, if the exact same convenience is applied to free falling objects in a vacuum,
but where does all the energy from mgh lifting things up go to?

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XPost: alt.sci.physics, sci.physics, uk.politics.misc

On 23 03, Jim Pennino wrote:

In sci.physics Dave <dwickford@yahoo.com> wrote:

Automotive brakes: these people obviously get cars to stop. So is the
heating proportional to velocity or velocity squared?

Who are "these people?

Brakes convert the kinetic energy of motion into heat.

The kinetic energy of motion is .5mv^2, therefor the heat is
proportional to the velocity squared.

<snip remaining clueless babble unread>

Thanks. Model cars can be used, to show that 0.5mv^2 is needed. Spending anything much is crazy (thought experiments are cheap). With full size
cars the v^2 from kinetic energy will be dwarfed by air resistance.

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On 03.01.23 15:55, Dave wrote:

<snip>

So, my expectancy is that if kinetic energy, and so gravity and a shed
more besides are wrong (E=0.5mv^2), physics across the planet will stop
being funded, since taxpayers don't fund kooks, and it is human nature
to throw the baby out with the bathwater. I'd give it 6 months.

Taxpayers have been funding kooks since the beginning of time and will
keep doing so til the end. How do you think politicians get paid?

<snip>

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XPost: uk.politics.misc, alt.sci.physics, sci.physics

In sci.physics Dave <dwickford@yahoo.com> wrote:

On 23 13, Dave wrote:

Electric car owners will have the luxury of knowing exactly how much
energy an acceleration cycle takes, and can compare and contrast.

To test this you can have an electric car very close behind a large
truck to reduce air resistance as much as possible. Really need a
private road for safety.

Electric cars don't have power or energy use meters, muppet.

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XPost: uk.politics.misc, alt.sci.physics, sci.physics

On 23 58, Dave wrote:

On 23 13, Dave wrote:

Automotive brakes: these people obviously get cars to stop. So is the
heating proportional to velocity or velocity squared?

Say a 2000kg car at 120mph (moderately high performance, not
exceptional, about limit of normal cars)
or 30mph.

30mph - 13.4m/s
120mph - 53.6m/s

at 30mph - kinetic energy is 0.5*2000*13.4*13.4 = 179,560 J
at 120mph - kinetic energy is 0.5*2000*53.6*53.6 = 2,872,960J

Don't think I'll ever get to find out anything from brakes.

However an airtrack (e.g. 12m) might be OK. How can kinetic energy be measured?

By doing work. e.g. lifting weights. Any temperature measurement has
too many inaccuracies. Need a kit with a hook to get caught by the car
with the wire connected via a pulley to a weight stack, and hopefully a
camera to film the high point, before it all comes crashing down.
Anything electrical needs full confidence in a whole lot more other
physics.

Giving different weights different accelerations and velocities should
be the easy part. Never got to use an airtrack at school or college.
The difference between kinetic energy and momentum is where you've lost
most people with physics.

Apologies for using usenet as a logbook, but there you go, don't like
secrets, and the other posters stop anything going too far off tangent.

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XPost: alt.sci.physics, sci.physics, uk.politics.misc

On 23 45, Jim Pennino wrote:

In sci.physics Dave <dwickford@yahoo.com> wrote:

On 23 58, Dave wrote:

On 23 13, Dave wrote:

Automotive brakes: these people obviously get cars to stop. So is the
heating proportional to velocity or velocity squared?

Say a 2000kg car at 120mph (moderately high performance, not
exceptional, about limit of normal cars)
or 30mph.

30mph - 13.4m/s
120mph - 53.6m/s

at 30mph - kinetic energy is 0.5*2000*13.4*13.4 = 179,560 J
at 120mph - kinetic energy is 0.5*2000*53.6*53.6 = 2,872,960J

Don't think I'll ever get to find out anything from brakes.

That's the first smart thing you've said in a long time.

However an airtrack (e.g. 12m) might be OK. How can kinetic energy be
measured?

You might start by doing some research on how the rest of the world does
it.

By doing work. e.g. lifting weights. Any temperature measurement has
too many inaccuracies. Need a kit with a hook to get caught by the car
with the wire connected via a pulley to a weight stack, and hopefully a
camera to film the high point, before it all comes crashing down.
Anything electrical needs full confidence in a whole lot more other
physics.

Nope, no research and off to la-la land you go.

Lots of things to check as well like the normal hard collisions, and
soft pickup, with minimum lost energy. e.g. a paddle.

If the kinetic energy can't do work then it isn't energy. It's something
else, which I don't know about.

You should be encouraging experimental physics instead of saying belief, belief. That's the difference between science and technology and religion.

A 60m vacuum drop is beyond my current budget, however. Anything much
less and differences between m/s^2, and m/s per meter won't be so clear.
Why are universities so scared of setting it up? Even with 9.8m/s^2 it
is good science for undergrads. Is everything looking at computer
screens now? Hopeless.

Giving different weights different accelerations and velocities should
be the easy part. Never got to use an airtrack at school or college.

So what? Low friction hobby wheels are dirt cheap.

The difference between kinetic energy and momentum is where you've lost
most people with physics.

Nope, mostly you.

This is a follow up from over 40 years ago. At school I asked the
teacher to explain again after class, and wasn't happy with the answer. Difference between KE and momentum.

Apologies for using usenet as a logbook, but there you go, don't like
secrets, and the other posters stop anything going too far off tangent.

Oh yes, science that has been well known over the entire planet for
about half millennium is just full of secrets, particularly to people
that don't understand math well...

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