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Feedback Comments on Friction

by Ron Kurtus

A total of 120 comments and questions have been sent in. They are listed according to date.

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

List of most recent 10 letters




Friction on Inclined Surface Object on a ramp USA
Uses of Friction Where is friction not needed? Swaziland
Causes of Friction Thinks gravity causes friction India
Sliding Friction Are comments true for sliding friction? Nigeria
Rolling Friction Wants resources South Korea
Changing Fluid Friction Does mass affect fluid friction? USA
Changing Sliding Friction on Hard Surfaces Which material lowers friction? Pakistan
Friction Equation Can friction be applied to time? Canada
Friction in Starting Rolling Motion Questions direction of friction force USA
Rolling Friction Need author name to cite article USA

Next 10


Object on a ramp

Topic: Friction on Inclined Surface


February 24, 2016

A 65.0 kg object is sitting on a 32.0 degres.The coefficient of friction present is .540.(Assume it will move down the incline).What are the values of the(a)WEIGHT force,(b)Normal force,(c)Parallel force,and the(d)Friction force?

Franck-Alain - USA



The normal force pushing the object to the surface of the ramp is N = mgcos(a), where m = 65 kg, g = 9.8 m/s^2 and the angle (a) is 32.

The resistance due to friction is Fr = Nfr, where fr = 0.54.

You can do the calculations.

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Where is friction not needed?

Topic: Uses of Friction


February 16, 2016

where is friction not needed?

siboniso - Swaziland



Friction is not needed if you do not want to stop or slow down a moving object.

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Thinks gravity causes friction

Topic: Causes of Friction


February 2, 2016

the main causes of friction is gravity present in earth. And i have full explanation of it but you should believe on me.

Abhishek - India



There is friction when you slide an object along the ground of other surface. The Earth's gravity causes the object to have weight and pulls it toward the other surface. The sliding of the surfaces results in the friction.

Gravity does not cause the friction but contributes to the effect. The friction in the brakes of a car have nothing to do with gravity.

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Are comments true for sliding friction?

Topic: Sliding Friction


January 9, 2016

are these below true of sliding friction?
-frictional force is independent of the area and dependent on the nature of the surfaces in contact.
-the frictional force is directly proportional to the normal force.

- Nigeria



The comments are true for sliding friction. Note that "normal force" is the force pushing the two objects together.

If you are able to read e-books, I can send you a file of the book either in the Kindle or in the EPUB format.

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Wants resources

Topic: Rolling Friction


December 23, 2015


I want to know the articles on this site information

Keyword : Rolling friction, plowing effect etc.


Jaebeom - South Korea



There are resources listed toward the end of the Rolling Friction page.

I hope that helps.

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Does mass affect fluid friction?

Topic: Changing Fluid Friction


December 10, 2015

So I was wondering is mass affected fluid friction. For example, if you had a 1 kg block compared to a 2 kg block, would there be more fluid friction if you dragged them through water?


Amanda - USA



The resistance in moving an object through the air or through water is dependent on the shape and size of the object. A 2 kg block would normally have more resistance than a 1 kg block. However, if the 2 kg block was streamlined, it could have less resistance.

If the blocks are sliding along a surface that is lubricated with water, the weight would be a factor.

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Which material lowers friction?

Topic: Changing Sliding Friction on Hard Surfaces


August 14, 2015

which of the following material lowers friction when pushed between metal plates option (a)water(b)fine marble powder(c) air(d)oil

muhammad - Pakistan



All of them would reduce the friction between metal plates. Oil is probably the best lubricant of the group.

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Can friction be applied to time?

Topic: Friction Equation


August 4, 2015

can friction be applied to time?

elizabeth - Canada



Friction can slow down motion. You could say that it slows down the time it takes for an object move some distance. So it indirectly is applied to time.

However, friction cannot be applied directly to time.

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Questions direction of friction force

Topic: Friction in Starting Rolling Motion


July 24, 2015

Subject: Friction resists sliding vs. Friction resists rotation

I think, a torque to drive the wheel and a pushing to pull the wheel has the same effect on the wheel. But the directions of two frictions are in opposite directions in your derivation.

I got the same results as you did. but I think somehow it is not correct. Because you can not tell which wheel is driven by a torque or a pull when you have many wheels in a train. If you say the friction resistors for some wheels are in one direction while for some other wheels are in opposite direction. We may have a problem.


Jack - USA



Thanks for your comments. I added some material to Role of Friction in Starting Rolling Motion to help clarify things.

The indicated friction is static friction resisting the rotation or spinning of the wheel. Combined with the force from the torque results in the force moving the wheel forward.

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Need author name to cite article

Topic: Rolling Friction


June 1, 2015

Hey, I cited some info from this page but, I need the author and publishing year in order to I text site it. If you could help me put I'd be very grateful.

Miranda - USA



Thanks for citing our article.
The author is: Ron Kurtus and the published date is: 11 March 2015.

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