Each day readers send in questions and feedback concerning the various lessons in the School for Champions website. A total of 15894 letters have been answered. They are listed according to date.
You can read them to further your understanding of the subjects.
|Center of gravity when standing on a ball||Physics||Gravity||UK|
|Why is ozone layer depleting?||Physics||Ozone Layer||Pakistan|
|How we can get rid of pollution?||Physics||Pollution||Pakistan|
|When is change significant||Machines||USA|
|Strategies plants use||Competition||Micronesia|
|Rubbing polycarbonate and polypropylene||Physics||Static Electricity||USA|
|Designed to travel faster than sound||Physics||Sound||USA|
|Rolling friction and area of contact||Physics||Friction||India|
|How to study||Grades||Nigeria|
|Good resource||Thanks||Physical Science||USA|
|Thinks of things in great depth||Senses||USA|
|I need a project on physics||Physics||Nigeria|
|Device using small disc magnet||Physics||Magnetism||Canada|
|Electrostatic induction and rice||Physics||Static Electricity||India|
Center of gravity when standing on a ball
September 20, 2017
If we are standing upright on the ball of one foot where would our centre of gravity be on our foot?
Athos - UK (28251)
The centre of gravity would be somewhere in the centre of the person. However, there would be a ling going from the COG to the point where the foot meets the ball.
Why is ozone layer depleting?
September 19, 2017
Why ozone layer is depleting and what can we do to recover it?
Aamish - Pakistan (28240)
The ozone layer or ozone shield is a region of Earth's upper atmosphere that absorbs most of the Sun's harmful ultraviolet radiation. Unfortunately, some chemical compounds, such as chlorofluorocarbon and Freon, used in air conditioners and refrigerators break down the ozone.
The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion.
Slowly over the years, the ozone layer has been recovering.
How we can get rid of pollution?
September 19, 2017
Q.1 How you are contributing in pollution causing agent.
Q.2 How we can get rid of pollution.
Q.3 Why there is much pollution in Pakistan.
Aamish - Pakistan (28244)
Causes of pollution include older automobiles that don't have pollution controls, factories that emit smoke and pollution, and people who burn items with no controls.
Government controls are usually required to reduce polluting automobiles and factories. Education of the public is also necessary to eliminate pollution-causing fires, such as burning trash and even tires.
Many countries--including Pakistan--are struggling with ways to reduce their pollution.
When is change significant
September 19, 2017
Is there a point at which a change in mechanical advantage is considered to be empirically significant? +/-5%? +/-7%?
Greg - USA (28245)
The actual mechanical advantage of a given configuration can have a tolerance variation according to how accurate it is measured. This would have to be taken into consideration when seeing how significant a change would be. I really don't have any numbers, because it depends so much on the configuration.
September 18, 2017
On a nostalgia site about Freeport, Texas--where I was a child sixty years ago--someone mentioned that she remembers just going outside and shouting to hear an echo. But that no longer works. I remember being able to do that as a child, too. Can someone say a little about how echoes work. Would I be more likely to be able to hear an echo in a rural setting than in an urban one?
Cece - USA (28239)
Typically an echo is sound reflected off a flat wall. This can happen in hallways in some buildings or outside a wall. Echoes can also be heard when sound is reflected off a cliff in a mountainous area.
However, weather conditions are cause echoes in a rural area, such as a fog bank across an open field.
Another factor is that children seem to have more sensitive ears, such that they can hear sounds and echoes that an adult cannot.
Strategies plants use
September 15, 2017
I need to know the strategies plants use to out compete other plants,such as rapid growth,chemical warfare,growing up over other plants,and shade tolerance.
Pelwin - Micronesia (28237)
You have listed many of the strategies plants use. See Competition Among Plants for details.
Rubbing polycarbonate and polypropylene
September 14, 2017
Will Poly-carbonate and polypropylene create static when rubbed together?
Jason - USA (28236)
It is possible that some static electrical charges could be produced, however the effect would be minimal.
Designed to travel faster than sound
September 12, 2017
How are objects designed to travel faster than the speed of sound?
Ali - USA (28230)
Aircraft that are designed to travel faster than sound usually have a relatively sharp nosecone to better cut through the air resistance and reduce the shock wave. Also, they have their wings slopped back to reduce that resistance and allow the air to flow around them.
Rolling friction and area of contact
September 11, 2017
Is rolling friction depend upon area of contact
How to prove that if yes or no with an
Rohan - India (28226)
The coefficient of rolling friction, ?r, isn't a simple number as in the case of sliding friction for hard materials. Instead, it is proportional to the width of the wheel and inversely proportional to the radius. In the case of soft wheels and tires, ?r the surface area of the tire on the ground is also a factor.
See: Coefficient of Rolling Friction.
How to study
September 11, 2017
how to study
Patrick - Nigeria (28227)
Your teacher will usually give you instructions of what to study. How to study means you read the material and try to understand it. Also, it is a good idea to take notes during class to use as a reference when you study, as well as when you take a test.
See Taking Notes in Class, as well as other lessons in the Good Grades section.
September 8, 2017
I was checking out your physical science resource page. I really like the Science Master resource! it's perfect timing with the book I'm reading on memory "Moonwalking With Einstein."
Drew - USA (28220)
I'm glad the resource was useful to you. Enjoy your book.
Thinks of things in great depth
September 8, 2017
Okay, so I feel like Im very different in a normal way though that it isn't normal....if that made any sense.
Its hard to describe so ill do my best but i always thought i just over think things way too much, like i mean I've always gone way into depth with things like to the point where it use to hold me back from things. For instance ill describe to my friends what I'm thinking of so well and use the best explanation possible they are mind blown and they always say to me "I would have never even thought about that but its so true".
Usually once I explain what Im thinking and why someone or an object did this, I always ask "have you ever thought about it like that" and they all say "No, this not normal to think that in depth, but what you said was so true i don't understand how you even thought like that".
So basically i say things that are so true and describe it so right. But according to my friends nobody would ever take the time to think that into depth with something so stupid or so simple or even complex.
Its weird cause I'm terrible with my words but when it comes to this i don't understand cause I'm terrible at describing things like how i feel about someone or telling someone my feelings. But its weird because i can't describe why i have this and why i guess its not normal They think i have a "magical power" or a "sixth sense" but i don't know if this is normal. or maybe it was just how i was raised but like i tell myself everyday how normal i am compared to people cause i can describe what people are thinking but in the same breath not in the way if someone came up to me and ask what am i thinking right now, i would have no idea what they are thinking that moment.
Its just weird cause i can get along and adapt to literally anyones personality even if they are crazy cause i know I’m normal and they won’t effect me cause i see everyones view points on things even if its not right but i can cope with them and get along because I'm so normal....? like i don't think when i tell my parents that I'm so normal like they don’t understand I'm not the average person i guess so many people are crazy and their thoughts aren't right and there is no reason for this but life.
I just don't understand how i can see things from other perspectives and know what everyone is thinking even if they haven't thought about the topic or subject really. I mean i guess thats the best way i can describe whats going on in my head over email but why do I feel this way?
jillian - USA (28221)
It sounds like you have a very analytic mind. There are jobs in business and science where such capabilities are in demand. However, a person needs to know when to stop and to draw conclusions. In some areas, it is known as "paralysis by analysis" where the person tries to dissect issues to the point of not taking action.
Probably, in most situations, you can't think of the right words to use, but in special cases where you are extremely interested, you can describe things well.
You might try writing down your thoughts and observations. That could be an effective exercise.
Also, look into job descriptions where companies are seeking people with analytical minds. You could be aiming at a good future career.
Best wishes on using your skills effectively.
I need a project on physics
September 8, 2017
I need project on physics
Abubakar - Nigeria (28222)
See our short list of Physics Experiments for some examples and ideas.
Device using small disc magnet
September 6, 2017
Good morning Ron. My son and I are developing a low tech medical device that relies on the attraction between a small disc magnet 20 mm x 2 mm and a similarly sized flat washer. We're having a problem with the amount of attraction between the two and need to increase it and are thinking about increasing the size of the magnet or the washer but are constrained in doing this due to physical dimensions. Is there anything readily available such as a flat washer or disc with a higher than normal iron content that would cause the magnet to be more strongly attracted to it? Many thanks!
Niall - Canada (28214)
You might try a Neodymium disc magnet. They are small, strong and inexpensive and can be bouht through Amazon.com or other outlets.
I hope that helps. Best wishes for success with your device.
Electrostatic induction and rice
September 5, 2017
Electrostatic induction or electrostatic generator that can stick with plain dry rice or not ???
daksha - India (28213)
An example of rice being affected by static electricity can be explained in Rice grains sticking to a polythene bag.
Questions and comments
Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. I will try to get back to you as soon as possible.
Share this page
Click on a button to bookmark or share this page through Twitter, Facebook, email, or other services:
Students and researchers
The Web address of this page is:
Please include it as a link on your website or as a reference in your report, document, or thesis.
Where are you now?