# The Naked Scientists Forum

### Author Topic: What is kE?  (Read 5322 times)

#### Thebox

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##### What is kE?
« on: 26/03/2016 10:36:37 »
Kinetic energy, a rather strange and mysterious concept that is seemingly mistaking displaced velocity for something else energy based.

When a roller coaster is lifted, the carriage gains relativistic mass, when the carriage is released it becomes a subject to gravity and falls down the track , when the carriage reaches the ground level instead of creating a force of impact (F=ma)  ,   the velocity is gradually displaced by the gradient of the track  , cushioning and deflecting the carriage taking away the impact.  No impact, no external stopping force and according to Newton the mass will remain in motion unless there is an acting external force.   When the carriage reaches the ground level it does not impact, it continues it's new velocity parallel to the ground where the grounds external force eventually brings the vehicle to an halt.

What do you think?

added- I drew it for you

« Last Edit: 26/03/2016 11:02:43 by Thebox »

#### Thebox

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##### Re: What is kE?
« Reply #1 on: 26/03/2016 11:17:35 »
Sorry got carried away with my art.

« Last Edit: 26/03/2016 11:23:52 by Thebox »

#### alancalverd

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##### Re: What is kE?
« Reply #2 on: 26/03/2016 13:39:47 »
As I have explained many times before, energy is a scalar, i.e. it has no direction. Velocity is a vector. So energy is conserved (mgh = œmv2) and momentum is conserved (ΔΣmv = 0). It's difficult to observe the latter since the two masses involved are the mass of the trolley and the mass of  the earth, but you have to take it into consideration when manipulating objects in free fall.

Note that the mass of the earth, me, is implicit in g, and v = ve + vt.

#### Thebox

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##### Re: What is kE?
« Reply #3 on: 26/03/2016 14:05:01 »
As I have explained many times before, energy is a scalar, i.e. it has no direction..

I have to disagree , energy  has isotropic  ''centrifugal direction'' ,   if it were not for electro-negativity  holding electro-positivity in place, the electro-positivity would just expand isotropically from itself leaving a negative void in the center.

A positive energy can not hold itself together without a negative hold to hold it together.

#### syhprum

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##### Re: What is kE?
« Reply #4 on: 26/03/2016 15:36:24 »
I find it difficult to believe that when one provides energy to move a body away from a source of gravitation that that body gains mass due to E=MC^2 ?

#### syhprum

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##### Re: What is kE?
« Reply #5 on: 26/03/2016 16:29:07 »
On further thought I have convinced myself, where does the energy come from to lift the roller coaster ? we break up a few Uranium atoms in our reactor and export the energy obtained hence the Earth must have become a little less massive.
We have a closed system so the roller coaster that receives that energy must have gained mass!.

#### evan_au

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##### Re: What is kE?
« Reply #6 on: 26/03/2016 22:24:58 »
Quote from: TheBox
a=9.81m/s2 ... linearly fixed velocity constant
The roller coaster trolley, while it is falling vertically accelerates under the force of gravity.
This means that the velocity is not fixed, but is increasing linearly.
And the distance fallen is increasing quadratically.

Quote from: TheBox
the carriage gains relativistic mass
Quote from: TheBox
electro-negativity  holding electro-positivity in place
While Einstein was able to make amazing deductions from imagining electric trolley-buses traveling near the speed of light, I think it is more sensible for you to first come to terms with the kinetic energy of electrically neutral trolleys traveling nowhere near the speed of light.

#### Thebox

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##### Re: What is kE?
« Reply #7 on: 27/03/2016 00:10:41 »
Quote from: TheBox
a=9.81m/s2 ... linearly fixed velocity constant
Quote
The roller coaster trolley, while it is falling vertically accelerates under the force of gravity.
This means that the velocity is not fixed, but is increasing linearly.
And the distance fallen is increasing quadratically.

My own fault for putting an ambiguity sentence, yes the speed increases per meter, but I meant that 9 .81m/s2 is a constant rate on earth but nether mind.

Quote from: TheBox
the carriage gains relativistic mass
Quote from: TheBox
electro-negativity  holding electro-positivity in place
While Einstein was able to make amazing deductions from imagining electric trolley-buses traveling near the speed of light, I think it is more sensible for you to first come to terms with the kinetic energy of electrically neutral trolleys traveling nowhere near the speed of light.

Electrically neutral does not mean that the trolley does not contain positive, kE sounds rather ''poppy cock''

What is kE apart from vivid imagination?

#### alancalverd

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##### Re: What is kE?
« Reply #8 on: 27/03/2016 00:42:21 »
What is kE apart from vivid imagination?
The purpose of physics is to build predictive mathematical models of things that happen.

Classical mechanics describes what happens to objects larger than a molecule, moving at substantially less than the speed of light, for periods between the big bang and the foreseeable future.

Three quantities are conserved in a classical interaction: mass, energy and momentum. Energy turns up in a number of forms, mostly as kinetic, potential and heat.

The formal concept of kinetic energy as œmv2 was a stroke of brilliance in the 17th century, though the relationship between KE and PE had been surmised thousands of years earlier and used by whoever invented the bow and arrow. The conservation principle has been understood and applied by every engineer from Newcomen to NASA.

The discovery of radioactivity added a twist as it seemed that energy could appear ex nihilo but it turns out that the small correction factor E = mc2 completely accounts for the measured mass loss in nuclear decay and the observed momentum of the daughter particles.

#### Thebox

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##### Re: What is kE?
« Reply #9 on: 27/03/2016 00:45:14 »

We have a closed system so the roller coaster that receives that energy must have gained mass!.

Relativistic mass relative to the ground.

+a=+F

An object at ground state will be x mass, raise the object and relative to the object it gains more Fn.

The speed of the fall creating an illusion that the object has gained something, the only thing gained is distance and falling acceleration Fn.

#### Thebox

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##### Re: What is kE?
« Reply #10 on: 27/03/2016 00:50:48 »
What is kE apart from vivid imagination?
The purpose of physics is to build predictive mathematical models of things that happen.

Classical mechanics describes what happens to objects larger than a molecule, moving at substantially less than the speed of light, for periods between the big bang and the foreseeable future.

Three quantities are conserved in a classical interaction: mass, energy and momentum. Energy turns up in a number of forms, mostly as kinetic, potential and heat.

The formal concept of kinetic energy as œmv2 was a stroke of brilliance in the 17th century, though the relationship between KE and PE had been surmised thousands of years earlier and used by whoever invented the bow and arrow. The conservation principle has been understood and applied by every engineer from Newcomen to NASA.

The discovery of radioactivity added a twist as it seemed that energy could appear ex nihilo but it turns out that the small correction factor E = mc2 completely accounts for the measured mass loss in nuclear decay and the observed momentum of the daughter particles.

What on Earth as that suppose to mean Alan with no disrespect intended, science seem to have invented their own language that doesn't come across in English.

Quote
Energy turns up in a number of forms, mostly as kinetic,

I don't get it, what ?

What is kE?

The rest energy of matter does not increase or decrease by motion, only  that which  is being absorbed or emitted changes relative to motion.  Force of impact increases with motion, +h (height)= + force,  +force delta direction = parallel distance travelled.

Ok, let us take a 1kg weight and raise it 2m in h,

F=ma

F=0.1*9.81m/s2

9.81m/s +  9.81 m/s = 19.62 m/s  when it hits the floor.

F=0.1*19.62 = 1.962N

So if we Y delta X at 0h , how far will the object travel X?

1kg + 2my = ?mx

Oh and by the way, F=0.1*0m is still 0.981N the same as 1m h which is a mystery.

Fn=h0= 0.981N = (F=0.1*9.81m/s and 1m h) which is wrong somewhere.

« Last Edit: 27/03/2016 02:36:35 by Thebox »

#### evan_au

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##### Re: What is kE?
« Reply #11 on: 27/03/2016 02:32:01 »
Quote from: TheBox
What is kE apart from vivid imagination?
If you get hit by a bus, it leaves very little to the imagination....
You wouldn't call the resulting damage poppycock!

Kinetic Energy = œmv2
If the bus weighs twice as much as a mini-bus (but traveling the same speed), the KE of the bus will be twice that of the minibus.
If the minibus is traveling twice as fast as the bus, , the KE of the minibus will be twice that of the bus.

Quote from: TheBox
The speed of the fall creating an illusion that the object has gained something, the only thing gained is distance and falling acceleration Fn.
Another few things that the fall has produced are:
velocity or speed
Momentum = m*v
Kinetic Energy = œmv2

Note: Normally, Force would be labelled F, and acceleration would be labelled something like a. For objects of constant mass, they are proportional.

Quote
Force of impact increases with motion, +h (height)= + force,  +force delta direction = parallel distance traveled.
The force of the impact is very variable over time, depending whether the object lands on concrete, water, feathers, or has its direction changed to the horizontal by roller-coaster tracks (and so effectively lands on air). It also depends strongly on whether the trolley is more or less rigid than the thing it runs into.

While the instantaneous force of impact is very important in designing crash-resistant cars, seat-belts and air-bags, this consumes a lot of supercomputer time (and crash dummies).

Most of the time, you can determine a lot from the momentum and kinetic energy of the impact. And you can ignore relativistic mass (which is so small for a roller coaster or a bus that we can't hope to measure it).
« Last Edit: 27/03/2016 02:47:08 by evan_au »

#### Thebox

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##### Re: What is kE?
« Reply #12 on: 27/03/2016 02:38:35 »

If you get hit by a bus, it leaves very little to the imagination....
You wouldn't call the resulting damage poppycock!

NO , I would call that force, the force of the bus was greater than my inertia, +speed = + force

No kE needed, next?

Quote
And you can ignore relativistic mass (which is so small for a roller coaster or a bus that we can't hope to measure it).

Huh? you already measure it .

Relativistic mass is what you call kE but which is really increased relativistic weight.

The higher you lift an object, the heavier it becomes relative to the ground, terminal velocity is the weight maximum limit and at its relativistic heaviest.

Take a 5kg object at ground state

0.5*9.81=4.905N

Now raise this object 5 m h,

0.5 * 49.05= 24.525n relativistic weight

Then convert 24.525n  into a ground state mass to get the equivalent.

24.525n = 2.5 mass  at ground state or 25kg approx

F=ma

2.5*9.81=  24.525n at ground state

« Last Edit: 27/03/2016 03:18:34 by Thebox »

#### evan_au

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##### Re: What is kE?
« Reply #13 on: 27/03/2016 03:12:18 »
Quote from: TheBox
I would call that force, the force of the bus was greater than my inertia
Well, here is another definition of Energy:

E = F*d
Where:
• E is Energy (measured in Joules)
• F is Force (measured in Newtons)
• d is distance (measured in meters)
Now, whether this Energy is Kinetic Energy or Mechanical/Thermal energy depends on how the bus applies the force:
• If you are leaning on a stone wall, and the bus runs into you, your velocity will not change (ie stationary). The energy of the bus will go into mashing you to a pulp.
• If you are crossing the street when the bus runs into you, your velocity will change dramatically (to pretty much the original speed of the bus). The energy of the bus will get turned into your kinetic energy, plus some mechanical energy in smashing a few bones, etc. In this case, you won't get pulped quite so much (at least until you hit the ground).

Quote
+speed = + force
Quote
1kg + 2my = ?mx
I suggest that you try to attach units to everything you do (like m/s2 in your diagram for acceleration). This often reveals errors in logic, for example when you equate speed (in m/s) with force (in Newtons), or attempt to add mass (in kg) to height (in meters).

There is a very real difference between Force (Newtons) and Energy (Joules). It is similar to the difference in a car between Torque (in Newton-meters) and Power (in Joules/second).
Car lovers want a car that has high torque and high power (and generally, the car manufacturers try to deliver both in the same vehicle).
But you could imagine:
• A car with very high torque but very low power: Great pushing down walls, but not much good for anything else (like a lightweight bulldozer)
• A car with very high power, but very low torque: Great for traveling at high speeds, but it takes 5 minutes to accelerate from 0 to 100km/h.
But if you can't see the difference, you are in good company. Michael Faraday didn't distinguish the two in his work - but then he was an accomplished experimentalist, and wasn't too rigorous about getting the maths right.

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##### Re: What is kE?
« Reply #14 on: 27/03/2016 03:44:57 »
If you think "pair production", say from some gamma photon decay (e-/e+) ...... and further realize, these particles are likely quantumly entangled i.e. meaning, to exact work on one, would correspondingly cause mutual energy increase in the other  - if by then, every particle in the universe has a partner, perhaps when we accelerate a given mass, may only be privvy to half the overall affect?

If the relationship between mass, energy and speed holds true (as in Einstein's iconic equation); maybe, it also applies to that of mass, energy & velocity  .... only that we merely 'see' 0.5 x the jazz?

Just speculative logic, man.

#### alancalverd

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##### Re: What is kE?
« Reply #15 on: 27/03/2016 11:00:17 »

The rest energy of matter

is irrelevant to classical mechanics, in which, by definition, mass is conserved.

#### Thebox

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##### Re: What is kE?
« Reply #16 on: 27/03/2016 11:03:38 »

The rest energy of matter

is irrelevant to classical mechanics, in which, by definition, mass is conserved.

And that means in plain English?

#### chiralSPO

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##### Re: What is kE?
« Reply #17 on: 27/03/2016 11:45:53 »

Huh? you already measure it .

Relativistic mass is what you call kE but which is really increased relativistic weight.

The higher you lift an object, the heavier it becomes relative to the ground, terminal velocity is the weight maximum limit and at its relativistic heaviest.

Take a 5kg object at ground state

0.5*9.81=4.905N

Now raise this object 5 m h,

0.5 * 49.05= 24.525n relativistic weight

Then convert 24.525n  into a ground state mass to get the equivalent.

24.525n = 2.5 mass  at ground state or 25kg approx

F=ma

2.5*9.81=  24.525n at ground state

No. You are on the wrong track here. I am not quite sure what track you are on, but it ain't right...

F = m*a means force = mass times acceleration
force is in units of Newtons (N = kg*m*s2)
mass is in units of kilograms (kg)
acceleration is in units of m*s2

therefore it makes sense that, for instance:
5 kg * 9.8 m*s2 = 49 kg*m*s2

it looks like what you are calling "relativistic weight" is probably work (force times distance) or potential energy (both expressed as energy)

energy (work) is in units of Joules (J = kg*m2*s2)

so the work required to lift a 5 kg object 8 meters up against Earth's gravity is:
8 m * 5 kg * 9.8 m*s2 = 392 kg*m2*s2 = 392 J

note that if we apply E = m * c2, (m = E * c2)
392 kg*m2*s2 * (299800000 m*s1)2 = 0.00000000000000436 kg = 4.36 picograms

so the relativistic mass for a 5 kg object raised 8 meters above the Earth, is 5.00000000000000436 kg

#### Thebox

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##### Re: What is kE?
« Reply #18 on: 27/03/2016 12:27:24 »

No. You are on the wrong track here. I am not quite sure what track you are on, but it ain't right...

A bit contradictory mate, you say you are not sure what I am talking about yet you claim it is not right.

Quote
F = m*a means force = mass times acceleration
force is in units of Newtons (N = kg*m*s2)
mass is in units of kilograms (kg)
acceleration is in units of m*s2

Huh?   why are you putting - 2

Force = mass times acceleration

force is measured weight , in Newtons,

a=9.81m/s2

which means that for every  meter falling it increases its acceleration *2

You lost me , I know what F=ma means, or I thought I did.

Let me confirm,

for 1kg mass we put 0.1 in the calculation for mass?

F= 0.1 * a

acceleration is 9.81m/s2

for the first  meter

9.81m/s

2nd meter

9.81m/s*2

3rd meter

9.81m/s*3

?????????????

#### syhprum

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##### Re: What is kE?
« Reply #19 on: 27/03/2016 12:30:35 »
I take it that if the energy to raise this 5Kg mass has come from an Earth bound source the Earth has also lost the same amount of relativistic mass.
Due to the daughter atoms from the spit uranium atoms having less mass and Neutrinos carrying off some.
« Last Edit: 27/03/2016 16:44:50 by syhprum »

#### Thebox

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##### Re: What is kE?
« Reply #20 on: 27/03/2016 12:36:30 »
I take it that if the energy to raise this 5Kg mass has come from an Earth bound source the Earth has also lost the same amount of relativistic mass.
Due to the daughter atoms from the spit uranium atoms having less mass

Not at all, the energy used to raise the 5 KG is independent of the 5 kg, the energy is made to raise the 5 KG.

In experiment let me offer this , in a scrap yard there is a drive on set of scales, a weigh bridge, that weights all the old scrap cars etc, so imagine we weight a car to reveal at ground state the car has a 1 ton mass, now raise the car 5 m and drop the car on the scales, I guarantee the scales will measure a huge mass difference when the car lands on the scales.

To me, science has got a lot of different things that mean the same thing.

Mass is equivalent to Newtons.  scratches  head....

Can we make these scales they would be well cool?

sorry

« Last Edit: 27/03/2016 13:06:24 by Thebox »

#### puppypower

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##### Re: What is kE?
« Reply #21 on: 27/03/2016 13:50:05 »
Kinetic energy is 1/2 MV2. In this equation, kinetic energy is a property of mass and velocity squared.

If we look at the velocity squared term, squaring a number not only impacts the scalar, but also the vector. Squaring means a plus or minus vector direction, ends up the same, in terms of kinetic energy. Kinetic energy is not relative to direction and therefore it is not relative to any given reference, since the vectors connected to red and blue shifts are normalized by the square term.

As an experiment, we can start in empty space with zero gravity and use X fuel to generate a final velocity for our rocket. This kinetic energy will be based on an energy balance; X fuel. We can launch the first experiment moving away from the earth and then the second experiment toward the earth. Based on energy conservation, since we used the same fuel both in all experiments, both experiment will have the same kinetic energy. However, special relativity calculations will show differences in motion coming and going, relative the earth. The slowing or speeding up of space-time, due to relative reference, does not alter fuel usage, energy conservation and therefore the kinetic. These only add an energy mask to the true kinetic energy.

The lack of dependency on kinetic enemy on reference, can also be inferred from dimensional analysis. If you look at the units of kinetic energy, it is M d2/t2. It is mass times, double the units of space-time (d,t). This tells us kinetic energy is not a function of one space-time reference, but rather of two references. The real kinetic energy, based on energy conservation, is not impacted by the red or blue shift seen by different references, who may see this motion coming or going.

Kinetic energy needs to be measured against a standard that is not connected to space-time; C-ground state. At the speed of light space-time breaks down, so one reference is possible for a standard. In space-time we need to use two reference and then take an average of sorts.

I often wonder if we are properly conserving energy, when we look out at space and see the Doppler shift using one space-time reference as the standard. The result of a red shift only approach; from earth reference, would take away energy. The result will be hidden energy that needs to explained in others ways; dark energy.
« Last Edit: 27/03/2016 13:52:24 by puppypower »

#### Thebox

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##### Re: What is kE?
« Reply #22 on: 27/03/2016 14:24:19 »

#### jeffreyH

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##### Re: What is kE?
« Reply #23 on: 27/03/2016 14:59:40 »
Mechanical energy, with the ability to do work, comes in two forms. Potential and kinetic energies. These are energies of motion and relate directly to the equation F=ma.

#### alancalverd

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##### Re: What is kE?
« Reply #24 on: 28/03/2016 00:32:10 »
I would call that force, the force of the bus was greater than my inertia,
Force is rate of change of inertia. You can't equate force with inertia.

Quote
And that means in plain English?
that the sum of the mass of the bus and the mass of your body is the same before and after the collision, even if bits of your body are distributed over the road and the bus. Provided the bus was travelling at less than 100,000,000 m/s, the relativistic correction is negligible for forensic purposes.

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##### Re: What is kE?
« Reply #24 on: 28/03/2016 00:32:10 »