# Science Feedback

by Ron Kurtus

Readers have sent in a total of 4986 comments and questions on Science issues. They are listed according to date.

## List of most recent 15 letters

### Country

Coefficient of friction on an incline Coefficient of Friction USA

Distribution of pressure Pressure USA

Relationship between math and science Using Mathematics Zambia

Solve for R-values Thermal Insulation Philippines

Is brick a better insulator than wood? Thermal Insulation UK

Convert heat to work Thermodynamics India

Food box insulation Thermal Insulation USA

Thanks for the page Motion Laws USA

Why is the atmosphere mostly heated by the earth? Heat Transfer on Earth Tanzania

How do I buy these lessons online? Force and Torque New Guinea

How does Physical Science apply to life? General South Africa

Why is ozone layer depleting? General Pakistan

How we can get rid of pollution? General Pakistan

Units of pressure and force Pressure India

Water pressure when stones added to a pool Pressure UK

Next 15 letters

## Coefficient of friction on an incline

February 17, 2020

### Question

When finding the coefficient of friction on an incline, is it helpful to go with the lowest value or should I take the average? Or both?

Hannah - USA (29361)

First there is static friction on an incline, holding back the object. Then once the object slides, there is sliding friction, which as a lower coefficient of friction. Typically, you only state the sliding coefficient.

## Distribution of pressure

February 5, 2020

### Question

Considering that Pressure is force over Area, i.e. If a place a 1,600 pound distributed over a bar of say a bar of 4 FT X 1 Ft weight -> the pressure in psi is calculated over the area of the bar.
I am told that If a place under the still bar (supporting the 1,600 pound weight) a 5 FT X 4 Ft a 1" thick playwood sheet / board the 1,600 Lb Pressure is then distributed over the area if the 5' X 4' area.

Is this correct ? Thank you for assisting an 80 year old engineer that is not clear on these matter.

Tony - USA (29345)

The pressure is distributed over the area in contact. The pressure from the 4 X 1 bar on the 5 X 4 sheet only concerns 1600 X 4 X 1. However, the pressure of the plywood sheet with the bar on top of it on the ground would relate to the area of the sheet.

## Relationship between math and science

February 13, 2019

### Question

What is the relationship between maths and science with example?

lesa - Zambia (28942)

You can learn about the various sciences with no mathematics at all. However, if you want to measure effects and make predictions, you need to use mathematics to make the calculations.

For example, you know that a ball will fall to the ground due to the force of gravity. That is science and physics. But if you want to know how long it takes to hit the ground from a certain height, you need to use the formula and make the calculations with the math.

I hope that helps your understanding. Best wishes for success in your studies.

## Solve for R-values

February 3, 2019

### Question

How did you solve for the R values?

Eron - Philippines (28935)

An R-value is the capacity of an insulating material to resist heat flow. The higher the R-value, the greater the insulating power.

An article that explains how to calculate the R-value is: What Does R-Value Mean?

I hope that helps.

## Is brick a better insulator than wood?

February 1, 2019

### Question

Is brick a better insulator then wood?

Tyler - UK (28932)

Since brick is very solid, it is not really a very good insulator. On the other hand, wood is a good insulator. For some information, see Brick Homes vs Wood Homes.

## Convert heat to work

October 31, 2018

### Question

Sir please comment my answer "conversion of heat energy into work".from the lesson thermodynamics.

Anjali - India (28775)

A common way to convert heat energy into work is in an engine. The gas inside the cylinder is heated and expands, thus moving the piston and creating work.

## Food box insulation

October 16, 2018

### Question

My question is about insulation for the firebox on a food cart I'm building. I want to prevent the outsides of the fire box from getting to hot. I want to enclose the insulation , not sure if that is the best way. I am working with food so I cant have particulates floating. I was going to use a ceramics insulater. Also should I paint the inside of the firebox first ? Flat paint or ? Thank you for your consideration.

Bill - USA (28752)

I'd like to help you, but for the life of me, I haven't been able to find good information on that. Perhaps checking with other fireboxes might give you some insight.

Best wishes on building your firebox.

## Thanks for the page

September 19, 2018

### Question

Hi,

My daughter Alice and I wanted to write to thank you for your page https://school-for-champions.com/science/motion_laws.htm . She's learning about force and motion in Science class, and it really has been very useful with her homework.

I have been trying to take a step back and allow her to take the reins in the hunt for useful research for her projects. For this project, your page was extremely helpful, though she also really likes this one: http://www.home-elevator.net/elevator-physics.php . I was so impressed when she suggested that her find would be good to add to the resources you already have, and I promised that I would write you to pass that idea along.

If you do decide to add it, please let me know :) Alice would be so excited!

Thanks again, and best wishes,
Nina (and Alice)

Nina and Alice - USA (28711)

I'm glad the lesson was useful to your daughter Alice. I added her suggested resource on the References and Resources of Newton's Laws of Motion.

Best wishes to Alice for success in her studies. I am sure she will do great.

## Why is the atmosphere mostly heated by the earth?

March 30, 2018

### Question

Why atmosphere is mostly hearted by the earth rather the sun

Halifa - Tanzania (28492)

Since the atmosphere is basically transparent, it is not heated much by the sunlight. However, the dark soil absorbs the radiation and become heated. Then air in contact with the ground gets heated through conduction. Then the other air is heated by convection.

Sunlight heating the ocean is not as effective as heating the ground, but it still is better than the air.

## How do I buy these lessons online?

March 23, 2018

### Question

James - New Guinea (28484)

You can use all of the lessons at no charge to you. I hope they help you in your studies.

## How does Physical Science apply to life?

January 29, 2018

### Question

How to really understand physical sciences and adapt to it in everyday life

Thapelo - South Africa (28408)

Physical Science includes Chemistry, where you can see how materials combine. It also includes Physics, where you can see how energy affect things and causes motion.

When you understand what causes things, you can then get an idea of how it applies to everyday life. See Physical Science Overview for more information.

## Why is ozone layer depleting?

September 19, 2017

### Question

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

### Question

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.

Thanks

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.

## Units of pressure and force

July 13, 2017

### Question

Why pressure and force unit is same?

Pratik - India (28131)

Pressure is force per unit area: P = F/A.

Units are Pascal = Newtons per square meter

## Water pressure when stones added to a pool

February 9, 2017

### Question

Ron, Thanks for your article. what happens to water pressure if some of the water is removed and replaced by stones. In a pool. I think the water pressure at bottom of pool is reduced.

Kieran - UK (27870)

Water pressure is caused by the weight of the water above the point of measurement. If the pressure is measured in grams per square cm, it would be the weight of the column of water 1 square cm times the height.

This would be true for water pressure at the top of the stones. Since the distance to the surface is reduced, the water pressure would be less at that point than at the bottom with no stones.

## Misc

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