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Feedback Blog

Each day readers send in questions and feedback concerning the various lessons in the School for Champions website. A total of 14975 letters have been answered.



List of most recent 15 letters

Title

Subject

Section

Country

Always getting shocks Physics Static Electricity Qatar
 
Making a Center of Gravity balance Physics Gravity USA
 
Falling objects on other planets Gravity USA
 
What does 750mA convert to amps? Physics Electricity USA
 
Does south pole of a magnet repel steel? Physics Magnetism Canada
 
How are gravity, velocity, and time related? Physics Gravity India
 
How are magnets made? Physics Tanzania
 
Application of magnetism in a transformer Physics Electricity Zambia
 
Prove in terms of relativity Physics Malawi
 
Great stuff Thanks UK
 
Using echo to measure speed of sound Physics Sound Ghana
 
Can I give my dog 5 aspirins at once? Animal Health USA
 
Wants good grades because of her dad Grades UK
 
re: Do objects hit the ground at the same time? Physics Gravity Netherlands
 
Factors contributing to health Grades USA
 

Next 15 letters


Always getting shocks

Physics

April 25, 2015

Question

Hi!
i have big problem now with my Body..if i touch any object even to people i got a electric shock ..rightnow,i am afraid to touch anything coz there is sparks or electric when to touch. Please help me? Why i got this ??when i was in the philippines i didnt encountered this kind of illness.

Gracel - Qatar (25949)

Answer

Static electric shocks can happen more when the air is dry, as it usually is in Qatar. However, in the Philippines, the air is more humid, which stops the shocks.

One thing that could be causing your problem is dry skin rubbing against your clothes. If you can, try some moisturizing lotion on your skin. Also, polyester clothing causes more shocks than cotton. See if wearing all cotton clothes helps.

You can use a metal key to touch metal objects such as doorknobs to drain off the electricity in your body.

Hopefully, these ideas will help. Best wishes on stopping the static shocks.

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Making a Center of Gravity balance

Physics

April 24, 2015

Question

Hi

Thanks for your explanation of Center of Gravity. All the examples are very good. I particularly like your illustrations..

I want to be able to build and balance something like a U-shaped bar:

---------------
l
l
l
---------------

How do I go about it?

I've seen it done on this YouTube Video. Please advance to the 5:23 minute point and onwards in the video. You see what I have in mind.

Question:

Do you first find the Center of Gravity of the connecting piece (the middle point?) and then the Center of Gravity somewhere in space between the two projecting pieces?

I need to build this for my grandson for a school project. I plan to use wood initially and if it works, I will do it in metal just as shown in the Youtube video.

Many thanks for your guidance. Much appreciated.

Cheers!

Anil - USA (25947)

Answer

The balanced u-shaped metal tubing piece in the YouTube video looked pretty cool. Note that he added some weight to the ends of the arms, so that the center of gravity (CoG) was not too close to the sideways beam. If the total weight at the end of the arms equaled the weight of the cross bar, then the CoG would be in about the middle of the U.

Here is my idea of how to do it:

First assemble the three parts of the U. Then tape a sheet of paper or thin cardboard over the U, in order to mark the CoG.

Attach a string to a point on the U and hang it from that string. The arms of the U will face somewhat downward. From that same point hand another piece of string with a small weight on its end. That string should pass through the CoG. You can mark a line on the cardboard around where the CoG would be.

Repeat that by hanging the U from another point and marking where the lines cross. That is the CoG of the U. You might have to do it a few times.

Then attach your wire hook to reach the CoG.

I hope this helps. Best wishes for a successful demonstration. Let me know how things turn out.

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Falling objects on other planets

Gravity

April 23, 2015

Question

Although my curriculum in College was dual (Electronics Engineering student and Liberal Arts), I was exposed to the fine points in Mathematics. Your exposition with respect to the 'Free Falling objects' will prod many to enjoy Mathematics! My question is:

Can the 'Free Falling' formula apply to gravity in relation to the other planets or is there another formula to calculate this theory?

Thank you.

Georges - USA (25942)

Answer

The equations for a freely falling objects assume that the object is relatively close to the Earth and the air resistance is negligible. This would also apply to objects on the Moon or other planets, using the value of "g" for the planet.

"g" on the Moon is 1/6 that on Earth, so you would use 32/6 ft/s^2. On a planet like Jupiter, there would probably be sufficient atmospheric resistance to be an added factor.

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What does 750mA convert to amps?

Physics

April 21, 2015

Question

What does 750mA convert to amps?

Jon - USA (25939)

Answer

mA means miliamps. "mili" is 1/1000, so 750mA = 0.75A.

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Does south pole of a magnet repel steel?

Physics

April 20, 2015

Question

Is it the North pole that attracts to steel and the south pole which repels to steel? Thanks.

Eric - Canada (25938)

Answer

The atoms in standard steel are randomly oriented, but they realign when a magnet is brought near the steel and cause attraction to the magnet.

If the north pole of a magnet is strong enough, the piece of steel can become magnetized and turned into a magnet itself. That means it would have a north and south pole, and the south pole of the steel would repel the south pole of a magnet.

However, the atoms in a piece of steel quickly get disoriented such that there is no direction preference. Then the south pole of a magnet would attract the steel, just as would the north pole of a magnet.

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How are gravity, velocity, and time related?

Physics

April 18, 2015

Question

how the gravity velocity time are related?
how the time on space and earth are different?

ATHULYA - India (25931)

Answer

See Derivation of Velocity-Time Gravity Equations for information.

The measurement of time is dependent on the velocity of objects. It only becomes different at extremely high velocities--close to the speed of light. In general, large objects in space do not travel that fast. However, some small particles do travel close to the speed of light, and time to them is slowed down.

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How are magnets made?

Physics

April 17, 2015

Question

What are methods of storing magnects?How magnets are made?How are they destroyed?

Melkior - Tanzania (25928)

Answer

There are natural magnetic materials, such as magnetite. Magnets can be made by rubbing another magnet against the material or by using an electromagnetic field. See: Magnets and Electromagnets.

Heating a magnet can destroy its magnetic ability.

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Application of magnetism in a transformer

Physics

April 16, 2015

Question

most of electrical equipment depends directly or indirectly on magnetism. without magnetism the electrical world we would perceive today would not exist (a)Explain the application on magnetism in a transformer with an aid of a simple diagram

fulko - Zambia (25924)

Answer

Magnetism and electricity are connected through electromagnetic waves. They do not exist independently. Magnetic fields create electric fields and electric fields create magnetic fields.

Thus, the movement of electrons in wires in one part of the transformer creates a magnetic field that creates movement of electrons in the other end of the transformer. The voltage of the electricity depends on the ration of the windings of thw wire.

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Prove in terms of relativity

Physics

April 16, 2015

Question

the explanation is so understandable!! great work

however how can u prove that in terms of relativity

patrick - Malawi (25926)

Answer

Relativity comes into play when the velocities approach the speed of light.

The work expended accelerating an object from rest to a relativistic speed is:

W = [mc^2/SQRT(1 - v^2/c^2)} - mc^2

The proof is too complex for these lessons.

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Great stuff

Thanks

April 15, 2015

Question

Hi Ron,

I was looking for some information on personal finances today when I came across your resources. Great stuff!

Michelle - UK (25921)

Answer

Thanks for the feedback. I'm glad it was helpful.

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Using echo to measure speed of sound

Physics

April 12, 2015

Question

can echo be measure by the velocity of sound?

inusah - Ghana (25914)

Answer

Echoes are often used to measure the velocity of sound.

If you know the distance to a wall or object and then measure the time it takes the echo to reach you after sending out a sound, you can calculate the speed of sound.

In this case: v = 2d/t, where d is the distance to the wall. 2d is used because the sound goes to and back.

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Can I give my dog 5 aspirins at once?

AnimalHealth

April 12, 2015

Question

for an eighty pound dog the dosage given was5 baby aspirins in a 12 hour Time span. How much can you give at one time In a single dose?

Jean - USA (25917)

Answer

Although some vets say you could give 5 baby aspirins at one time, it is much better to start off small and and spread them out to avoid adverse reactions.

I assume you want to give aspirin to relieve pain, such as from arthritis. Thus it is better to start with one on two baby aspirins to see how well they work, as well as if there is a reaction. Certainly, any aspirins should be given with food and water.

Aspirin should only be used as a temporary relief, such as if the dog is crying from pain, It should not be used as a regular routine, because it can result in stomach ulcers.

The best thing to do is to check with your vet, who may prescribe a different medication.

Best wishes for your dog's health and comfort.

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Wants good grades because of her dad

Grades

April 11, 2015

Question

I just wanted to know how to get good grades because of my dad and see the tricks to it

Tahiya - UK (25909)

Answer

Although your dad may want you to get good grades, the most important thing is that you want good grades to feel good about yourself. They are also important for your future.

You can look through the lessons to get ideas to improve in different areas, such as doing homework and doing well in tests.

Set a goal of what grades you want to get. Write them down on a piece of paper that you can check as a reminder.

The fact that you want good grades is a first important step in achieving your goal. It shows that you have it in you to succeed.

Best wishes on getting top grades in school.

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re: Do objects hit the ground at the same time?

Physics

April 11, 2015

Question

Appreciate for your response but i would like you to refer from this discussiom "http://physics.stackexchange.com/questions/10773/how-does-gravity-affect-bullets". Referring to a long range gun, accordingly if im not mistaken, it is possible that an object may orbit the earth with the right velocity and force applied to an object. So it is possible that they will not hit the ground....

Priori - Netherlands (25910)

Answer

For relatively short horizontal distances, the objects will hit the ground at the same time. But if the bullet travels far enough, the curvature of the Earth becomes a factor. If the projectile velocity is great enough, it can orbit the Earth or even go into space. See: Newton's Cannon for an example of this with illustrations.

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Factors contributing to health

Grades

April 10, 2015

Question

1.explain factors contributing to health and unhealth body condition 2.explain importance of the good health

rich - USA (25907)

Answer

See Factors Involved in Physical Health and Preventing Physical Diseases for your information.

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