Coefficients of static friction in shows

Lab: Measuring Coefficients of Friction

 

Purpose:

• To determine whether tread design affects the coefficient of static friction for running shoes

 

Materials:

• Meter stick
• Wooden board
• 7 examples of shoes

 

Hypothesis:

• I hypothesize that the tread design will affect the coefficient of static friction of the shoes.

 

Procedure:

• Collect observations of each shoe: size, heaviness, width, and a brief description of what the tread looks like.
• One by one, place each shoe on the wooden board, and raise one side until the shoe begins to slide downward. Take measurement of angle of inclination. Repeat 3 times for each shoe so as to maintain accurate data.
• Repeat step 2 measuring data for rough side of wood as well as smooth side.
• Use angle of inclination to solve for each shoe’s coefficient of static friction between its tread, and the wooden board.
• Use all data gathered to disprove or confirm hypothesis.

 

Observations:

Shoe descriptions:

1. Skater shoe: mildly heavy shoe, tread is flat and worn down with wavy pattern through it
2. Running shoe #1: very lightweight shoe, tread is thick and in 2 separate blobs, and also worn down to make it more flat.
3. Running shoe #2: also very lightweight shoe, tread is thick and has texture, also in 2 blobs, not much tread is touching the surface of the wood.
4. High heal shoe: medium weight shoe, tread is very flat, thin and in 2 sections.
5. Male dress shoe #1: Heaviest shoe, tread has slight texture, but otherwise very flat and very widespread.
6. Male dress shoe #2: Semi-lightweight shoe, tread has texture and is curvy.
7. Sandal: Heavier shoe, tread is wavy and blocky.

Wood description: 58cm long, 30cm wide, one side is rough and other side is smooth.

 

 

 

 

 

Observations chart:

Shoe	Surface	Test1	Test2	Test3	Test Average	Coefficient of Static Friction
1	Smooth	26°	24°	23°	25°	tan q =mu \tan 25=0.47 \mu = 0.47
1	Rough	53°	54°	53°	53°	tan 53 = 1.32
2	Smooth	45°	46°	44°	45°	tan 45 = 1.0
2	Rough	46°	50°	49°	49°	tan 49 = 1.15
3	Smooth	45°	48°	49°	48°	tan 48 = 1.11
3	Rough	49°	50°	47°	49°	tan 49 = 1.15
4	Smooth	25°	31°	27°	27°	tan 27 = 0.5
4	Rough	37°	38°	40°	38°	tan 38 = 0.78
5	Smooth	42°	41°	43°	42°	tan 42 = 0.9
5	Rough	53°	54°	52°	52°	tan 52 = 1.28
6	Smooth	31°	33°	31°	32°	tan 32 = 0.62
6	Rough	36°	37°	36°	36°	tan 36 = 0.73
7	Smooth	40°	41°	39°	40°	tan 40 = 0.84
7	Rough	47°	48°	49°	48°	tan 48 = 1.11

*Test1, test2, and test3 are all the observed angles of inclination.

 

Analysis:

Through analysis of the data that I have collected in this experiment, it is apparent that it is not the tread itself that makes a change in the coefficient of static friction, but the type and heaviness of the shoe itself. Though it does provoke a very miner change, it does not prove my hypothesis to be even remotely possible given the data shown in my observations. Ways to improve the quality of this data could be if we were to lengthen the board to get a more accurate angle of inclination, or possibly having an even wider range of shoes might make a difference in results.

 

Conclusion:

            In conclusion, my hypothesis was proved incorrect due to the fact that the data did not show a change due to tread, but a change due to shoe type and weight. So therefore, if shoe designers care about the coefficient of static friction of there shoes they should look at these factors and not at the tread itself.

Physics of the Centrifuge

This is the paper that I wrote for a physics class on centrifuges I thought why not post it on my blog:

Physics of the Centrifuge

 

            The basic description of a centrifuge is any type of device that uses centrifugal force to push an object outward. This paper will discuss how they do this, and some applications of centrifuges being used around the world today. We will also discuss the cost of them and how common they are in society, as well as the impact they have had on individual users, and on society in general.

 

            First let’s look at centrifugal force. This plays a key role in the design and use of a centrifuge and is essentially the objective of a centrifuge. What I mean by this is that the goal of a centrifuge is to achieve a high degree of centrifugal force acting on the object in question. A real life example of this type of force is if I have a bucket full of water, and I spin it in a circle quickly, the centrifugal force will push on the water, and at the same time the bottom of the bucket will keep the water from spilling out of the bottom. Centrifugal force is actually the opposing force to the centripetal force that keeps an object in circular motion. We can calculate this force using the following formula,

F=(m x v^2)/r, where “F” is centripetal force, “m” is mass of object in circular motion, “v” is the velocity of the object, and r is the radius or distance from center of the centrifuge to the object in motion. Since centrifugal force is the opposite of centripetal force, we use the same formula; only the resulting force must be negative.

 

            Therefore, a centrifuge machine basically does the same thing as my arm with the bucket of water, spinning an object rapidly in a circle. A common application of this is in a lab, when scientists must separate a mixture due to the density of the substances, they will use a centrifuge to spin a test tube rapidly, and since this increases the gravitational force on the substance inside, the more dense substances will go to the bottom of the mixture leaving the less dense substances on top.

 

            Another common application of this is when testing greater forces of gravity on a human being. Centrifuges simulate the affects of a pilot pulling up quickly when flying a plane, or when an astronaut is in a rocket being launched into space. Both of these scenarios increase the force of gravity due to the fact that as gravity is pushing down, they are rising up at a high velocity. So, to simulate this in a centrifuge, you use the person as the water in the bucket going back to the example from before. Using centrifugal force as gravitational force by spinning a capsule containing a person attached to an arm made of some kind of metal rapidly, you can simulate what it is like to have gravity increased to a level in which a person may black out due to the gravitational force pushing the blood from there brain down toward their feat.

 

            Designing a centrifuge is not as complicated as some might think due to the fact that the purpose is not as complicated as some might think. Though, there are many factors that come into play when looking at how it is run on the inside. Using a series of gears, powered by some sort of generator we can create the circular motion needed, and increasing or decreasing the speed all depends on the size of the gears. One factor that plays a key role when looking at rotation at high velocity is friction. Some type of lubricant must be used to reduce friction on the parts so that the constant and intense motion of metal on metal does not create heat energy, which would destroy the inner workings of the machine. 

 

            There are certain applications of centrifugal force where there are no actual centrifuge machines, such as our bucket and water example, but not just simple applications like that. I am talking about at amusement parks. Almost every ride you see at an amusement park usually deals with using centrifugal and centripetal force to give people the ride of their lives. Especially when looking at a ride that has multiple loops. These rides usually use the velocity at which you are traveling to create centrifugal force, which in turn, keeps you in your seat.

 

            The cost of a centrifuge varies from centrifuge to centrifuge. One for testing people will cost several millions of dollars where as a centrifuge testing the density of a mixture will cost only a few hundred dollars. There applications are well worth any price though if it is crucial for scientific research. That is why they are quite common in science labs and test facilities. It really all depends on what is being tested.

 

            In conclusion, the impact that centrifuge technologies have had on individuals and society in general has been a very good impact. They help scientists in ways that no other machines can, and they have helped to train pilots and astronauts so that when they are actually in the sky, they will know what to do when in a situation of extreme gravitational pull. They have had no negative impact at all really since their invention, and hopefully will help in new discoveries for science in the coming years.

 

            

Introduction

OK so hello my name is Peter Vlasveld and this blog is being created for me to have a more formal blog than the random blabber that I post on "Boring Blog of Peter Vlasveld". I will post papers in physics that I write. I am writing one this weekend about centrifuges which I will post.

This will be a science based blog and will contain all of my non-classified work in science. Meaning that I will post things that I am able to post without worrying about people taking it and... doing things with it. So yes this will be much more of a formal blog meaning actual thought out researched papers and whatnot. Possibly even interesting to read but I really don't know. I am an ammature writer and scientist so anyone who is more experienced and happens to come across it on the web can give there insight and even if you are not experience what so ever you can still tell me what you think so.. happy blogging everyone

Edit: I forgot to mention on a sidenote that this is also a skeptical blog so you may see me write more formal entries about my skeptical view on things.