The resistance a surface or object encounters when moving over another.

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Running Euler's disk in a superfluid

I was considering the toy Euler's Disk, a video can be found here: http://www.youtube.com/watch?v=mVl2CBG_h2s I was interested in understanding the behavior of the disk particularly in vacuum and in ...
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3answers
36 views

Cause of rolling friction

Can you explain the cause of rolling friction? Can you tell me why, while driving a bicycle, there is less rolling friction when its tyres are fully inflated?
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18 views

Dependence of kinetic friction on relative velocity

While I was reading my book I came across a line that tells that there is slight dependence of kinetic friction on velocity of relative motion of the bodies. Can anyone tell me how is this so?
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24 views

Frictional loss of matter

How do we account for the loss of matter from an object due to friction ? Is it simply a phenomenon or result of any other process ? Eg :The loss of matter from the rubber tyre
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37 views

Inclined pulley with unknown hanging mass: when won't the system accelerate?

We have an inclined pulley with angle of $30° $ a block with mass of $10 kg$ placed upon it and It is attached by a rope over a pulley to a mass of $M_A$ which hangs vertically. If $μ_s=0.4$ and ...
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1answer
46 views

Problem of uncoupling a train

As a kid I have seen several movies, cartoon etc. in which usually one guy just uncouple (unplugs (?), dunno) the rest of a running train and then runs off with the locomotive at full speed and ...
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4answers
91 views

Can the weight of a bird be measured, considering air friction? [duplicate]

Assume that a bird of mass 1.5 kg is held in a box at height 500m and this setup is placed on a weighing machine. Now, the bird starts to hover in the box pushing the air downwards, and is at a ...
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1answer
25 views

What forces cause the centripetal acceleration in circular motion on a merry-go-round?

Suppose you stand on a merry-go-round spinning at $f$ revolutions per second and you are $R$ meters from the center. What forces act on you? If you were tied to a rope like in Fig 2 you would follow ...
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1answer
28 views

Frictional force require to balance leaning sticks

Here is the question (from Morin's Introduction to Classical Mechanics book): One stick leans on another as shown in Fig. 2.21. A right angle is formed where they meet, and the right stick makes ...
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0answers
20 views

Inclined plane, circular motion and the friction

Suppose we have a cylinder on an inclined plane of mass $m$ and radius $R$ moving without sliding (so that $\varepsilon = a/R$). Why is the friction $F$ causing the circular motion sometimes lower ...
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1answer
16 views

Is weathering a form of friction?

Suppose I have a surface out in the wild somewhere. Let's suppose further that over time, this surface is eroded due to any typical form of erosion / weathering. Is this weathering due to a cumulative ...
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1answer
32 views

Problem on coefficients of friction? [closed]

How to approach problems where both coefficients of static and kinetic friction are given? Like in this: A 42 kg slab rests on a friction-less floor. A 9.7 kg block rests on top of the slab, ...
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30 views

Theoretical Question about a Frictionless Rope

This is kind of ridiculous to imagine, but say a person could somehow tie a frictionless rope into a knot. After making the loop and everything, and tightening the knot, technically the knot would ...
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1answer
28 views

Why, in a car taking a sloped curve, friction is perpendicular to the car

In solving the problem we usuallly use the friction as the centripetal force, but I could never understood how is this possible. I understand that if a car is making a circular motion, some ...
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1answer
105 views

How does a bowl of hot water move by itself?

I think everyone should have seen a bowl of hot water moving by itself on a flat surface such as glass(seems like it is moving by itself but maybe there are some external force applied to it when it ...
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1answer
39 views

Superhydrophobic coating and water friction

If you were to apply super-hydrophobic coating to the hull of ships or even submarines, would you get more or less water friction? If the coating completely repels the water you could argue there ...
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4answers
483 views

What is the cause of rolling friction? & why is it less than sliding friction?

Rolling friction is the resistance to motion experienced by a body when it rolls upon another. It is much less than sliding friction for same pair of bodies. When one body rolls upon another, there ...
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1answer
3k views

Why are dishwasher washed glasses “squeaky clean”?

They seem to have increased friction after going through a dishwasher. The unpleasant (to me) squeaky feel is probably slip-stick friction exciting resonance in the glassware. But why? What has ...
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3answers
76 views

Why do Signs Fall?

My question in this post is, why do signs with large angles fall? For example, fold a piece of paper in half, set the angle between the two halves, and place it on the floor; it will stand or collapse ...
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1answer
42 views

Why is it that friction apparently decreases with speed? [duplicate]

Whilst thinking of a trick where a magician pulls a tablecloth directly from under a full set dinner (a classic) I wondered why friction doesn't increase as speed does. I get that they use a pretty ...
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0answers
11 views

Calculate the distance travelled by hot air before it looses its momentum

Hot air is released from a nozzle with certain velocity into the atmosphere. As the stream travels, it looses momentum and after some time mixes with air.How can we calculate the distance the stream ...
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5answers
471 views

Force required to drive car

From what I know of Newtonian Mechanics, if an object is moving at a constant velocity, the net force acting on that object is equal to zero. If there is friction, then the applied force required to ...
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1answer
45 views

Rate of Temperature Change due to Heat addition

I might be wrong but I will give a little background leading to my question. I am trying to calculate the heat generation in the advection-diffusion equation for heat generation due to friction by ...
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2answers
25 views

Damping Constant for a Ball Rolling in a Bowl

How would you find the damping constant of a ball rolling without slipping in half of a sphere? I know how to find the period of the oscillation, but how would I find the damping constant ...
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1answer
24 views

Maximum velocity on Unbanked roads and why should friction be more than centripetal force? [closed]

Why is maximum velocity on unbanked circular road given by $\sqrt{urg}$ where $u$ is coefficient of friction, $r$ is radius of circular track and $g$ is acceleration due to gravity? Why should ...
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1answer
82 views

Lagrangian and Hamiltonian EOM with dissipative force

I am trying to write the Lagrangian and Hamiltonian for the forced Harmonic oscillator before quantizing it to get to the quantum picture. For EOM $$m\ddot{q}+\beta\dot{q}+kq=f(t),$$ I write the ...
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93 views

Friction Between Liquid and Solid Surface

How does friction between liquid surface and solid surface differ from viscosity, the friction between liquid and liquid surfaces? Also has a word describing the process been invented or is ...
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1answer
31 views

Where is the direction of kinetic friction in this question?

Suppose there is on object of 20.0kg sliding to the right. A person exert a force of 30N left on the object. The object has an acceleration of 2.5m/s^2 left. What is the magnitude and direction of ...
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1answer
52 views

Physics Forces and Friction [closed]

I'm working on this problem for my college physics class. It has to do with forces and friction and I want to make sure I go about this problem in the right way. I believe my teacher said that this is ...
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1answer
53 views

Why friction is not reliable for circular turns on horizontal road with high speed and sharp curve?

Why is friction not reliable for circular turn on horizontal road for centripetal force when high speed and sharp curve are involved? So banking of road has to be present to introduce a new force $N ...
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1answer
64 views

Finding Acceleration of Two Masses in an Ideal Pulley [closed]

I am stuck on this problem: Two masses are connected by a string which goes over an ideal pulley. Block A has a mass of 5kg and can slide along a rough plane inclined 30 degrees to the horizontal. ...
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1answer
52 views

Friction force in rolling motion

In rolling without slipping motion we know that the friction acting is static friction and so we treat it as an unknown while solving equations of dynamics. Is the static friction during pure rolling ...
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4answers
600 views

Why doesn't centrifugal force appear on an FBD for a car on a banked track?

Suppose you wish to find the max speed at which a car can travel on a banked curve of radius R and angle theta to the horizontal and coeff. of static friction mu. I don't understand the relevant ...
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1answer
88 views

The direction of frictional force in smooth rolling motion

I want to ask about the direction of frictional force in smooth rolling motion which means the rolling object doesn't slide on the surface. Here is the first case, the wheel rolls to the right so the ...
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1answer
331 views

Rolling with slipping [closed]

A tundra buggy, which is a bus fitted with oversized wheels, is stuck in Churchill, Manitoba, on slippery ice. The wheel radius is 0.86 m. The speedometer goes from 0 to 27 km/h while the buggy ...
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2answers
38 views

When an applied force that exactly equals the max static friction is on an object

When an applied force that exactly equals the max static friction is on an object, does the object start moving at this point?
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2answers
47 views

Does drag produce heat?

When a solid object moves through a fluid drag is produced. Does this drag produce heat? I believe drag should produce heat as it is the friction between fluid and surface of object. Is this true or ...
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3answers
59 views

Model of contact friction

Consider the standard model of kinetic contact friction taught in introductory physics courses: $$F_f=\mu_k*F_N$$ According to this model, for a block with initial speed $v$ moving on a horizontal ...
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1answer
58 views

When we are walking or running, which friction is exerted on our feet? Kinetic or static?

As already mentioned in the title, when we are walking or running on the floor, which friction is exerted on our feet? Kinetic friction or static friction? In my understanding, the answer is static ...
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1answer
87 views

Finding Static Friction of Car Going Around Curve [closed]

The question is: A 1200 kg car is traveling along a curve 250m in radius and is moving at a speed of 10m/s but is lowing at a rate of 2m/s^2. What is the static friction force on the car as a ...
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1answer
49 views

Friction because of Earth's rotation

Is there some force of friction that acts on bodies due to rotation of Earth. We all know earth is an non inertial frame. If there is some frictional force is there some way to prove it. What i mean ...
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1answer
52 views

Is it possible to eliminate Van der Waals interactions?

I came to know that the friction force actually depends on the surface contact area due to weak interactions (adhesion due to Van der Waals forces) between the atoms of both materials increasing in ...
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2answers
82 views

Force balancing - Newtonian mechanics [duplicate]

If a horse pulls the carriage, the carriage should pull the horse with equal force (Newton's third law), then how does the whole system move? I drew the free body diagram but not yet figured what ...
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1answer
52 views

Work energy and laws of motion and friction problem?

I am having a confusion in the following question- Q-To stimulate car accidents auto manufacturers study the collision of moving cars with mounted springs of different spring constants. consider a ...
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5answers
4k views

Why are a motorcycle's front brakes more effective than back?

I've noticed that when I apply the front brakes on my bike it stops quite quickly. If I apply the back brakes at the same speed, it skids rather than stopping quickly. Why?
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2answers
105 views

Confusions in the 'Adhesion Theory of friction.'

While reading about the Adhesion theory of friction on this site, I came to some points which I couldn't understand. I have highlighted them: ...Adhesion approach is based on the partial ...
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1answer
89 views

A question about a body moving in horizontal circular motion

I have some related questions about a body moving in uniform horizontal circular motion: The body moves with a constant angular velocity on a rough horizontal surface. It is attached to a string that ...
4
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3answers
934 views

6 wheels more efficient than 4 wheels?

Which would be easier to push in a straight line, a flat cart with 4 wheels or the same cart (and same load) with the same size wheels, but has six wheels? and why? Thanks
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5answers
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How fast would someone have to run to travel vertically up a wall?

I am currently doing a physics project on the effects of so-called 'super-speed'. I was wondering how fast you would have to run to vertically travel up a wall? That is, to negate the force of ...
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1answer
59 views

How to model a very simple spinning wheel

First off, I'm not a physics person, just a lowly software engineer with below average math skills. What I've written is a simple animation of a spinning wheel using C++/GTK/Cairo. It allows the user ...