by Ron Kurtus
Readers have sent in a total of 876 comments and questions on Physics issues. They are listed according to date.
You can read them to further your understanding of the subject.
|Properties of good insulators||General||USA|
|Doppler effect||Visible Light||India|
|Time to reach the ground||Derivation of Velocity-Time Gravity Equations||India|
|Confusion on thermal energy||Thermal Potential Energy||USA|
|Static charges and slugs||Static Electricity Shocks||UK|
|Distance sound travels||Sound Echoes||Bangladesh|
|Relationship between magnetic force and electricity||Electromagnetism||Nigeria|
|Instantaneous velocity and acceleration||Acceleration||India|
|Difference between vaporization and sublimation||Dry Ice||Kenya|
|Reducing permanent magnetism||Basics of Magnetism||New Zealand|
|Top spin in golf with driver||Golf||USA|
|Contents of Gravity and Gravitation||Gravity||Nigeria|
|Biology vs Physics||General||USA|
|Wands free books on EMF||Magnetic Materials||Ethiopia|
Properties of good insulators
February 1, 2019
what are some good properties of good insulators.
ruben - USA (28933)
Certainly, a good insulator should hinder outside heat transfer (hot or cold). But also, the insulator must not weigh too much or take up too much space.
January 31, 2019
What will happen if object travels at half the speed of light. Is doppler effect applicable for electromagnetic waves?
Pankaj - India (28930)
Time to reach the ground
January 27, 2019
I have seen an equation to calculate time of an object to reach the ground as
Can you please help understand how this equation has come
Srinivasan - India (28924)
The time it takes a falling object to reach the ground is t = SQRT(2h/g) where h is the height or distance to the ground.
See Gravity Time Equations for Falling Objects for information.
I hope that helps.
Confusion on thermal energy
January 15, 2019
My question is the following:
It has to do with the idea of thermal energy being a sum of both the kinetic and potential energy of a material. Because I am teaching 8th grade Science at the time, I am trying to keep this as simple as possible. However, a student asked if two samples of air (one at approx. 0 Celsius, and the other at approx 27 Celsius) have different amounts of potential energy? After reading more about it, my thought would be no, they would have the same potential energy, just different amounts.
Rebecca - USA (28916)
The definitions of thermal kinetic energy and potential energy can be confusing. I updated the whole section to try to clarify issues and make it easier to understand.
What is called Internal Energy is the sum of the Thermal Kinetic Energy and Thermal Potential Energy.
See the updated versions of Thermal Energy is Kinetic Energy and Thermal Potential Energy.
The potential energy of two sample of air at different temperatures would be approximately the same. However, since the atoms or molecules travel faster at the higher temperature, the kinetic or thermal energy would be greater for the higher temperature.
I hope that helps. Best wishes for success in your class.
Static charges and slugs
January 14, 2019
Hello. I want to find a combination of materials that will hold a static charge for as long as possible to repel slugs and snails from a planter.
I have bought a copper braid copper adhesive strip for the purpose, but I want to find out that if I was to line the inside circumference of the planter with 15mm copper pipe and induced a very low current,(not enough to kill them, but enough to see them off)how long would either the static charge last as environmental conditions would influence this as well as a battery charge. Any help would be appreciated, thanks
mark - UK (28913)
One of the methods to get rid of with static electricity is explained in: How do I Get Rid of Slugs and Snails in my Garden? listed under "Give them a shock".
The method states that since slugs leave a slime trail, by using copper tape the slugs will get small electric shocks from the static electricity caused by the copper-slime combination.
The electric charge would only hold while the slug is moving along the copper tape.
I hope that helps. Best wishes in getting rid of those pests.
Distance sound travels
November 20, 2018
the sound of echoes is heard after 0.12 sec.what is the distance between the source and the reflecting surface when temp of the place is 30 degree Celsius
nasiba - Bangladesh (28840)
The velocity of sound in air at 30 degree C is: 349.4 m/s. (see Speed of Sound in a Gas).
The distance traveled in 0.12 sec is then 41.9 m. Thus, the distance between the source and reflecting surface is 1/2 of that or about 21 meters.
Relationship between magnetic force and electricity
October 23, 2018
my question is, what is the relationship between magnetic force and electricity?
Abdulrahman - Nigeria (28756)
See Moving Electrical Charges Create Magnetic Field. It shows that when electrical charges move, they create a magnetic force field. Likewise, a magnetic force can create electricity. See Basics of Electromagnetism.
Instantaneous velocity and acceleration
October 15, 2018
what is the difference between instantaneous acceleration and instantaneous velocity?
sona mariam - India (28749)
Instantaneous velocity is the velocity of an object in motion at a specific point in time, as opposed to the average velocity.
Average acceleration is the change in velocity over a period of time. Instantaneous acceleration is the acceleration of an object in motion at a specific point in time.
Difference between vaporization and sublimation
October 11, 2018
Differentiate between vaporization and sublimation
Kevin - Kenya (28745)
Vaporization is the process that occurs when a chemical or element is converted from a liquid or a solid to a gas.
When a liquid is converted to a gas, the process is called evaporation or boiling.
When a solid is converted to a gas, the process is called sublimation. This is what happens with dry ice (frozen carbon monoxide gas).
October 8, 2018
what is in the iron that makes magnetic substance attracted by it
obed - Ghana (28741)
It is the alignment of the electrons. See: Factors Determining Magnetic Properties.
Reducing permanent magnetism
October 6, 2018
If you have a weak permanent magnet and wind a multi turn coil around it and then pass an electrical current through the coil, can you negate the magnet strength of the magnet?
Will a specific current be required to reduce the magnet strength to exactly zero?
Charlie - New Zealand (28738)
You can demagnetize a permanent magnet by hitting it with a hammer or heating it to a sufficient temperature. Both cases disrupt the alignment of the atoms.
The problem with using a coil is that the atoms can be realigned into a different direction, thus still maintaining the magnetism. The only way to reduce the strength of the magnet is to get some or all of the atoms in random orientation.
Top spin in golf with driver
September 6, 2018
How can you impart top spin with a driver so that it can roll farther?
Ted - USA (28692)
You probably want a top spin so that the ball will roll further. You can do that by either topping the ball when you hit it or by changing your stance such that you hit the ball on the upswing.
However, most golf experts say that you will get greater distance with a driver by hitting the ball flush.
Contents of Gravity and Gravitation
July 23, 2018
Can you provide the table of contents in your physics book Gravity and Gravitational? I would like to know what I'm to learn in the book before buying to prepare for my O level examination.
Damilare - Nigeria (28636)
You can look at the web pages Gravity and Gravitation for listings of the topics in the book.
Although it is nice to have an actual book that you can refer to, the website lessons provide another choice, especially to be able to search and jump to different topics.
I hope that helps. Best wishes for success in your O-level examination.
Biology vs Physics
June 19, 2018
Hi. I am 14 and I’m in 8th grade. I finished middle school this year. And this fall I will be in high school. Next semester I will be taking biology is it harder than physics ?
Zoe - USA (28590)
Biology often consists of many fact about the various plants and animals. Physics often includes math and equations.
Typically, Biology is offered in the sophomore year in high school, while Physics is taken in the senior year. Both are interesting subjects and are worth taking.
Best wishes for success (and fun) in high school.
Wands free books on EMF
May 30, 2018
Hello I am bereket, age 20 and I'm from Ethiopia. I want to ask you how I can get free online books on EMF.
Bereket - Ethiopia (28571)
There are some free downloads on EMF from Free Books - EMF.
I'm not sure how extensive they are, but they might give you what you want.
Best wishes for success in your studies.
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