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Each day readers send in questions and feedback concerning the various lessons in the School for Champions website. A total of 15899 letters have been answered. They are listed according to date.

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

List of most recent 15 letters





I like this site very much Thanks India
Force between mother and child Gravitation India
Tough problems Gravitation USA
Suggested resource Finances USA
Objects in contact exert force on each other Physics Gravitation South Africa
Is period related to density? Physics Motion India
Thanks for making this site Thanks Machines UK
Resources helpful for students Web Design USA
Class of lever of pressure cooker Machines USA
Resource from Girl Scout Finances USA
Why don't we realize the inner parts of the ear? Senses USA
Where is air on the list? Static Electricity Russia
Too many x-rays? Health India
Protons and radioactivity Matter India
How does CO2 liquid turn to a solid? Matter India

Next 15 letters


I like this site very much


January 20, 2018


I like this site very much.

Prince - India (28394)


I am glad you like the site and it is useful to you. Tell your friends about the website.

Best wishes for success in your activities.

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Force between mother and child


January 19, 2018


What is the gravitational force between mother weight 50kg,child weight 1kg,are separated a distance 2m

Lavanya - India (28393)


F = (6.674*10^-11 N-m2/kg2)(50 kg)(1 kg)/(2 m)^2

F = 83*10^?11 N

See Gravitational Attraction Between People.

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Tough problems


January 18, 2018


Hi Ron, nice web site, well done. I hope the following 2 questions are within your scope of knowledge because I'm interested in your thoughts.

1) If the earth and moon were released from rest at their present distance of separation R, what would be their distance of separation as a function of time, and how long would it take for them to collide? Assume all speeds are non-relativistic and neglect drag from the sloshing of the oceans and any other types of drag.

2)solve the following equation for x:


Thanks Champ! Sincerely,

Wayne - USA (28391)


1. If the Earth and the Moon were allowed to fall toward each other, the force of attraction would vary according to 1/R^2. That means the force would be increasing until they collide. Finding the separation is not simple and requires knowledge of Calculus. Unfortunately, I don't have that derivation or the equations readily available.

2. y = (x^3) - (4/x) can be rearranged to be x^4 - xy - 4 = 0. The "y" factor makes it difficult to solve. If y was a function of x, you could used the quadratic formula to solve for x.

Sorry, that's the best I can do

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Suggested resource


January 18, 2018


Hello Ron,

I hope you're having a good day!

Your list was really informative. I'm currently doing some article research about student loans and credit cards and these resources was a great help!

I wonder if you can consider these added, I found some updated loan lenders that might be helpful for other students too, I hope you can check it out (If you have time):

1. Best Student Loans

2. 9 Best Companies for Student Loan Refinancing and Consolidation in 2018

All the best,

Rachel - USA (28392)


Thanks for you suggested resources. I added them to the Finances Resources page.

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Objects in contact exert force on each other


January 14, 2018


Hi Ron please clarify the following....why is it that two objects that are in contact do not exert the force of gravity on each bcz they both have mass and their centres are distance apart.

Sidanga - South Africa (28389)


When two objects are in contact, they each exert the force of gravity on each other. The main example is what an object is in contact with the Earth, where gravity between them affects them both.

But one reason it is noticeable is because the mass of the Earth is so great. If the objects are normal size, there still is an attraction, but it is almost too small to measure.

See Cavendish Experiment to Measure Gravitational Constant to see the measurement between objects.

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Is period related to density?


January 14, 2018


Is the Time period of simple pendulum is directly proportional to density. Please explain.(while Time period does not depends on mass)

Mallikarjun - India (28390)


The period of a pendulum is independent of the mass of its bob. (See Pendulum Exhibits Periodic Motion.)

The density of the bob or weight equals its mass divided by its volume. Since the period is independent of the mass, it is also independent of the density of the bob.

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Thanks for making this site


January 12, 2018


Hey thanks for making this site.

Aidan - UK (28385)


I am glad the material has been useful to you. Best wishes for success in your studies.

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Resources helpful for students

Web Design

January 11, 2018


Hello, School for Champions,

I came across your site while researching for an article I'm working on for my web design project.

I just want to say thank you for keeping all these resources on one page. You're making it easier for us readers/student to find exactly what we needed. By the way, I did happen to find another good webpage on the same topic you are covering. You might want to check it out (If you have free time):

1. How to make a website with WordPress - A guide that will help you out setup your website in less than an hour with just 5-easy steps.

2. Best WordPress Hosting 2018 - A good comparison of web hosting sites depending on your needs.

I know you are busy and probably get millions of emails a day, but hopefully, this one could help other students struggling with the same topic. Again, thank you for your help and for providing great resources.

I hope you have a great day! :)


Ellie - USA (28382)


Thanks for the suggested resources. I added them to the Web Design Resources page.

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Class of lever of pressure cooker


January 5, 2018


Pressure cooker is which type of class lever? Can we say pressure cooker simple machine?

Bhima - USA (28376)


Since a pressure cooker has no moving parts,, it could be considered a form of simple machine, where heat creates an internal pressure.

However, it is not a lever and really has no moving parts. But the heat can create pressure and a force.

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Resource from Girl Scout


January 3, 2018



I'm Amy Clarkson a mom of three amazing kids. I'm reaching out to you because recently, my youngest Peyton is a scout and is working towards earning her money management badge. We spent a couple of days searching the web for resources. Thankfully, we came across your page . It was very helpful - thank you!!

In return Peyton wanted to share with you this page, Financial Literacy . It's a guide to money management and financial literacy. She was thinking it would make a you should add it to your page, what do you think?

Whether you add it or not we wanted to say thanks!! If you do decide to add it, please let me know! She would be happy to see it was added and also would show her fellow scouts :)


Amy - USA (28372)


Thanks for the suggested resource. I added it to the Finances Resources page.

Best wishes for Peyton's success, as well as your other children.

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Why don't we realize the inner parts of the ear?


January 1, 2018


If our ears have so many parts inside ,three bones, cochlear etc . then why we don't realize them when we hear any sound? What is the mystery behind this?

Koushik - USA (28371)


These parts do not have any extra sensors to indicate their use when you hear. It is similar to not realizing the various parts of the eye when you see things.

You realize the output for which the ear, eye, or other sensor is intended.

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Where is air on the list?

Static Electricity

December 28, 2017


Thank you. It was very interesting and informative. I have seen an other list, where the line is little bit different. But anyway, I have one question, where in this three lists will be air?

Mikayel - Russia (28368)


The triboelectric series mainly concerns materials rubbing against each other, so often air is not mentioned. However, lightning is caused by air and water in contact.

The website Triboelectric Series includes air at the top of their list. However, there is no mention of water. I'll try to find water in some other list.

Meanwhile, I added air to our Static Electric Material page list.

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Too many x-rays?


December 26, 2017


I am a 31 year old person and my chest x-ray done by a doctor two times in a month.I want to know that there is any risk or not for my body.


Narendra - India (28367)


Having x-rays two times a month seems excessive unless it is to monitor a fast growing ailment. Ask your doctor if having x-rays twice a month is really necessary.

Being 31 years old, you need to make sure your reproductive organs are protected by lead shielding.

If the x-ray equipment is modern, the radiation is much smaller, and the risk is less. However, it still is best to not have the x-rays unless really necessary.

Best wishes for good health.

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Protons and radioactivity


December 24, 2017


How much proton are in radioactivity element generaly.

- India (28365)


Proton emission (also known as proton radioactivity) is a rare type of radioactive decay in which a proton is ejected from a nucleus.

Protons are usually emitted along with neutrons as Alpha-particles.

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How does CO2 liquid turn to a solid?


December 22, 2017


How does co2 liquid converted into dry ice

vignesh - India (28361)


The atmospheric pressure for CO2 to be a liquid must be high--over 5 atmospheres. Then the liquid will crystallize similar to how liquid water turns to ice.

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Next 15 letters


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