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Physics Feedback

by Ron Kurtus

Readers have sent in a total of 846 comments and questions on Physics issues. They are listed according to date.

You can read them to further your understanding of the subject.

List of next 15 letters




Where are the attractive forces equal? Force Between Two Objects USA
Connecting AC to terminals of a battery AC India
Why aren't mercury lamps used more often? Lighting India
Where do charges go? Basics Zimbabwe
Wants to know about particle physics General USA
Viewpoint on gravitation and Big Bang theory General Bangladesh
Solenoid and electromagnet Solenoids India
Give examples of using force Forces Malaysia
Using adapter between plugs AC World Voltages New Zealand
How fast is a magnetic impulse? EM Waves USA
Is time static? Time USA
Thoughts on Absolute Zero Temperature Limits USA
Approved fuel containers Basics of Static Electricity Australia
Torque and increased diameter Force and Torque USA
Annoying ad on page Units of Frequencies and Wavelengths USA

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First 15 letters

Force Between Two Objects

Where are the attractive forces equal?

August 5, 2017


At what distance from the earth should an object lie between the earth and the sun such that the attractive force of the earth on it is equal the attractive force the sun on it , given that the distance between the earth and sun is 150million Km and the mass of the sun =3.24mass of earthh

- USA (28163)


The point where the attractive forces are equal is at the center of mass (CM) between the Earth and the Sun. See CM between two spheres for the equation.

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Connecting AC to terminals of a battery

July 26, 2017


What will happen if we connect Alternating current to the terminals of a battery?

Krishna Priya - India (28141)


You really can't charge a battery directly with AC electricity. An AC to DC adapter is needed.
It is also possible that the battery would become overheated from the AC and even explode.

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Why aren't mercury lamps used more often?

July 26, 2017


Why we use mercury lamps more often?Is there any beneficial thing about it?

Kanchana - India (28142)


A mercury-vapor lamp uses an electric arc through vaporized mercury to produce light. The light can be very bright. The advantages is that they are more energy efficient than incandescent and most fluorescent lights. One disadvantage is that they give off ultraviolet radiation, which can be harmful to the skin and eyes. Special filters must be used.

Mercury lamps are used for large area overhead lighting, such as in factories, warehouses, and sports arenas as well as for streetlights.

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Where do charges go?

July 21, 2017


where does the charges go when an object losses its static charges.

snobbo - Zimbabwe (28139)


Objects usually lose static charges on their surfaces by coming near an object with opposite charges. For example, if an object has negative (-) charges on its surface, and an object with an excess of positive (+) charges comes close, the negative electrons will jump to join with the positive charged ions to neutralize the charge.

Remember that a stable atom has a positive nucleus and negative charged electrons in orbit around the outside.

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Wants to know about particle physics

June 27, 2017


I am 70 years old. Since I've retired, I decided to enrich my brain studying science. In my studies the subject of physics was touched upon. I fell in love with particle physics! I took some chemistry about half a century ago. I would like to learn more about particle physics without going into the math. Can my poor old brain learn?

Don't know if you can answer. If not, I'll keep on searching!

Deborah - USA (28106)


It is great that you want to enrich your brain by studying the sciences. As they say, "It's never too late to learn."

I have several lessons on the basics of particle physics at Particles of Matter.

Also, you might find some articles of interest at Understanding Chemistry.

Best wishes on increasing your knowledge.

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Viewpoint on gravitation and Big Bang theory

June 19, 2017


Near about 14 billion years ago Allah/God the big bang and started evolution, now 7 divisible gravitation worlds.

“Gravitational worlds, they are moving or changing the orbit with their all family members depending on the nuclear of each other”. In this way- There has been incidence of full view of the universe at the very exact copy/invitation of the visible diagram solar system in the gravitation world. The universe has seven divisible, the first one of which is unit and the rest six are collective. The collective six gravitation are three invisible and the rest three are visible. The visible gravitation worlds are stars, planets and minor planets. The invisible gravitation worlds are black holes of various energy levels, the first one of which is the primordial black hole or Allah/God of the nuclear fusion of the universe. There have been collective six gravitation divisible of the big bang in future from the big black hole or Allah/God. At the first phase or level of the divisible is the black hole of the nuclear fusion of the clusters of galaxies or black hole named quasar. The second phase gravitation world of the quasars in future are of the black hole named pulsar or nuclear fusion of the cluster of galaxies. The third gravitation world of the pulsars in future is of the last black holes or nucleus of galaxy or the nuclear fusion of the constellations.

New Discovery of the Universe:

Pope: The most important news- about the God, Big Bang & Evolution at

Shahidur Rahman - Bangladesh (28099)


Thanks for the information and interesting viewpoint on gravitation.

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Solenoid and electromagnet

June 13, 2017


Why solenoid is used for making electromagnet

Nishant - India (28091)


A solenoid is an electromagnet without the iron core in it. The solenoid can be used to pull a core inside it.

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Give examples of using force

June 12, 2017


Name one examples when force can stop motion.

Name one examples when force can change the shape and size of an object

Nicholas - Malaysia (28088)


You can push on a rolling cart to stop its motion.

You can compress a foam rubber ball to change its size and shape.

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AC World Voltages

Using adapter between plugs

June 11, 2017


can I use an appliance from south Korea - 220v in New Zealand 230v ? from your chart it would also appear that the frequency will be different also will this cause problems? thirdly the plug types are different is it ok for an electrician to change the plug from c to l

Tina - New Zealand (28086)


The voltage difference should not affect things. However, a 60Hz appliance might perform slower with 50Hz. If there are timers or clocks involved, it might make a difference. It is good to check with the manufacturer website to see if things would work sufficiently.

An adapter plug could be used if the prongs are different. An electrician should be able to make the proper connections.

Best wishes for successful use of your appliance.

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EM Waves

How fast is a magnetic impulse?

June 3, 2017


Have the effects of magnetism (attraction-repulsion) ever been quantified into speed? How fast is a magnetic impulse?

James - USA (28072)


Magnetic, electrical, and gravitational impulses all move at the speed of light. Typically, a magnetic disturbance will cause an electrical disturbance, resulting in an electromagnetic wave, which also travels at the speed of light.

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Is time static?

June 2, 2017


Love your site, Thank You!

Subject: Relativity/Time
We humans understand time as past, present and future.
The Past is our Memory
The Present is our Current Condition
The Future is our Expectation

Is it possible that Time is static?

We exist in a series of static universes that we register as the duration or "flow" of time.
Even at Planck time there is duration.
Duration is change in the Universe.
By splitting any change into time segments, every change has a beginning, a duration and an ending.
Even the emission of a photon.
It is a static photon, it starts to move, continues to move and stops moving when acted upon or reaching the desired destination (Planck Length).
During the moment when it starts to move there is duration between its static point and its next static point.
There is even duration between the change of static points. Like a buildup to change similar to a potential charge of time. I'll call it a Duriton.
Duritons occur faster than can be measured by our technology. Just because something can't be measured doesn't mean it can't exist.
Our lives are a series of duritons that we register on a massive scale to simulate continuity.
Is it safe to say that we exist in a constant flow of individual duritons, remembering the past as the present?

Thank you.

tMic - USA (28069)


The whole concept of time is difficult and complex.
As far as humans go, the sensing of time seems to vary with age. See Sensing Time. Thus, is time different for different people?

At the quantum level of matter, movement is in "quantum jumps" instead of being continuous. Likewise, since time is related to motion, it too could be in quantum increments. Thus, you could think of time being static in between those jumps. Your idea of a "Duriton" might fit within that area.

In some theories, time is considered a fourth dimension. It can curve just as space can curve.

Keep up the good work in pondering these issues.

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Temperature Limits

Thoughts on Absolute Zero

June 2, 2017


Subject: Energy/Absolute Zero

"At the physically impossible-to-reach temperature of zero kelvin, or minus 459.67 degrees Fahrenheit (minus 273.15 degrees Celsius), atoms would stop moving. As such, nothing can be colder than absolute zero on the Kelvin scale."

However, is there a scale that measures colder than Zero Kelvin (Absolute Zero)?
Lets call that True Absolute Zero (TaZ)

We know that matter is composed of energy and the reversion of matter to energy is the basis of the atomic bomb. If matter is made of energy then is there a scale that measures energy down to its baseline?

An electron volt (eV) is not a baseline value of energy because we measure fractions of eV. Lets call the baseline value of energy an "Eneron".

Every atom has movement within itself on diminishing scales.
Quarks, Leptons and even Bosons have movement in their spins.
Temperature is movement. Frozen means no movement. True Absolute Zero would imply that all movement has stopped.

Energy implies movement. "Its energetic"
At TaZ (True Absolute Zero) wouldn't energy stop? If an Eneron stops, is it no longer energy. Can it restart without another Eneron acting upon it?

"The first law of thermodynamics, also known as Law of Conservation of Energy, states that energy can neither be created nor destroyed; energy can only be transferred or changed from one form to another."

If the Eneron stops it is no longer energy and thus the first law of thermodynamics is wrong.

In the Universe there exists a potential for everything to eventually and completely freeze over time. Everything in existence reaches true absolute zero and all energy stops. With no energy to initiate movement (heat), there is no action to generate more energy.

Thank you

tMic - USA (28070)


The requirements for Absolute Zero are not only that atoms stop moving or have zero kinetic energy, but also that their internal potential energy is zero. In reality, the binding forces of the atoms would reach zero, such that the particles would fall apart.

Even Quarks, Leptons, and Bosons would not move or spin.

Matter is really not made of "energy". The energy released in an atomic bomb, such that the mass of the material is reduced, is in the form of electromagnetic radiation or photons. These particles do not have a rest mass, but they do have momentum as they move.

An electron volt is the unit of energy equal to the work done on an electron in accelerating it through a potential difference of one volt.

I hope that gives some explanation. Keep up the good work in creatively looking at these Physics concepts.

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Basics of Static Electricity

Approved fuel containers

May 12, 2017


Hi guys

I am an ex firefighter (28 years) and are now involved in teaching fire safety. I deliver training to fuel company staff. One of the topics covers using the correct "Approved Fuel Containers" for transport of fuel (Petrol).

My question is, are the containers manufactured of a plastic that incorporates a conductive substance to dissipate electrical charge? If they are that is great but, my thoughts are they are as conductive as any other plastic container. If this is the case, how does the electrical charge dissipate when filling the fuel container on the ground. In theory it is non-conductive.

My thoughts are that all plastic will conduct electricity to a degree. Not enough to allow enough current to flow to power a light bulb if used in a circuit but will allow enough current to flow causing a static spark. I am thinking milliamps as compared to amps will flow.

I am attempting to confirm that the only difference between an approved fuel container and a non-approved fuel container is its solid construction of plastic that will not deteriorate by petrol.


Fred - Australia (28044)


Static electricity consists of electrical charges on the surface of the container. Approved Fuel Containers usually are made of a hard plastic material that does not collect charges as mush as a container made of a soft plastic. You can tell by rubbing a balloon on the container and see if it gets charges such that it sticks to some surface.

The big concern is having charges collect on the container and getting a static spark that would ignite the fuel fumes. If the container is on the ground and you are also on the ground, you are both "grounded" such that charges readily flow to the ground. But if the container is on a plastic bed of a truck when being filled, a spark may jump from the container to you are the filling tube, thus igniting the fumes.

Note that the issue isn't whether plastic conduct a little electricity, but is it whether charges on the surface will jump and cause a spark to some other item or person on the ground.

It isn't a simple situation, and I hope this clarifies things somewhat (or does not confuse the issue!)

Best wishes for success in your fire safety classes.

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Force and Torque

Torque and increased diameter

May 6, 2017


Im interested in torque on a round object.
I'd like to know if you increase the diameter of the object by say 10% how does it affect rotational torque.

Jon - USA (28038)


Since T = FR, increasing the diameter by 10% increases the radius R by 20%. Thus, the torque T would increase by 20%.

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Units of Frequencies and Wavelengths

Annoying ad on page

May 2, 2017


While on the page using Chrome on a Mac, the page is regularly refreshing and jumping around, making it very difficult to use.

The video ad in the upper right cannot be turned off, and is very distracting.

I like your material very much--you are clear, give enough information without assumptions as to how much a person knows and progress clearly. Thanks!

Stephen - USA (28033)


Thanks for the feedback.

The ads on my site are through Google AdSense and are not supposed to be annoying. I also hate going to websites where they have videos with loud sound. You typically can click the Pause button on the lower left corner to stop the sound and video.

If that does not work, let me know what company the ad is from, and I'll contact Google to block them from my site.

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