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Answers to Readers' Questions on Physical Science:

Changing Hard Sliding Friction

The following 4 comments and questions have been sent in. They are listed according to date.

List of first 10 items

• Could you provide some mathematical questions?
• High quality surface roughness can reduce friction
• Increasing the surface roughness
• Best lubricant to launch a steel ship

Next 10

Could you provide some mathematical questions?

Question

October 16, 2007

If you also provide some mathematical questions after every topic, it would be great.

Orion - India

14552

Answer

Thanks for the suggestion. We are working on adding more math to the sections.

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High quality surface roughness can reduce friction

Question

March 16, 2006

How finishing a job in the mechanical workshop to high quality surface roughness can reduce friction?

Moh'd - Oman

10475

Answer

Friction increases with rough surfaces. When you make one surface smooth, the friction will be less even if the other surface that it rubs against is still rough.

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Increasing the surface roughness

Question

March 14, 2006

if the roughness of the surface is increased beyond a limit, how will the coeffficient of friction behave ?

raghav - India

10436

Answer

As the surface roughness increases, the coefficient of friction increases. But it is not a linear increase. Also note that it is the relative roughness of both materials that determines to coefficient.

I am not sure what you mean by "beyond a limit." What limit?

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Best lubricant to launch a steel ship

Question

January 26, 2006

I am a naval architect. I would like to know the best lubricant to launch a steel ship, stern first as normally, where the sliding surfaces are wooden boards. I have liberty on the breath of each one of the two top boards but I am restricted to a length of 40 m on these boards. I would like a lubricant that would allow the minimum of inclination of the ways. The lauching weight would be about 800 tons. A starting push can be considered. The launching can be arranged to take place in Summer.
Your sdvice would be highly appreciated

Carlos - Portugal

9815

Answer

I'm sorry, but we don't have than information. I imagine that most naval vessel ship building companies would have such information. Also, the Portuguese navy should have specifications on what lubricants they require for launching ships they purchase.

Best wishing in finding your answer.

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