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Questions tagged [friction]

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

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3
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1answer
603 views

Circular motion, kinetic friction and tension

Hi: I've read this post: Uniform Circular Motion w/ Tension and Friction and helped me a lot. I have a similar problem: At one end of the rope ($R = 1 m$) is tied a mass ($m = 3 kg$) and the ...
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1answer
21 views

Velocity of the point of contact when we are walking

I know friction applies the forward push needed to walk (without slipping). Can we say that the point of the contact ( on the backward foot?) when we are walking will be at rest wrt the ground in much ...
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1answer
61 views

Is rolling friction enough to make a car turn?

I will distinguish between to kinds of frictions. When the car is moving in a straight line, the tire pushes the road backwards and the road pushes the car forward. Because of the friction between ...
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5answers
3k views

Finding the acceleration of a mass/pulley system without knowing the direction of the displacement

I have the following question: I noticed that if I solve for the acceleration assuming that the acceleration is occuring to the left, I get the equation: $\displaystyle a = \frac{m_3g-\mu_km_1gcos\...
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1answer
9 views

Horizontal component of velocity in case of rolling

I was having a hard time to understand that the point of contact in case of rolling without sliding has zero velocity. So after some research, I posted my understanding as an answer How can the ...
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1answer
997 views

Blocks and pulleys problem with friction - the condition for sliding

I encountered a problem with blocks and pulleys, which I'm not sure about. The diagrams I've drawn are given below. We need to find the minimal mass $M$ of the block $3$, such that block $1$ starts to ...
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2answers
216 views

Uniform Circular Motion w/ Tension and Friction

So I had a problem today which I couldn't make any sense of. I don't have access to it at the moment but this is a pretty accurate approximation. Basically, a mass (m) is swinging horizontally on ...
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6answers
3k views

Why does low tire pressure increase friction?

I've always thought that it was because the frictional force on the tire was increased due to the bulging of the tires increasing the surface area in contact with the road. However, a colleague of ...
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4answers
65 views

Find angle at which the boxes would begin to slide [closed]

The angle θ increases causing the box of mass $m_2$ to slide. Calculate at what angle the box begins to slide. Friction factor = 0.25 ; $m_1 = 15 kg$ ; $m_2 = 25 kg$ I am having difficulty ...
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1answer
50 views

Do the balls keep moving forever?

In a hypothetical world where there is no friction, and all collisions are elastic would an object in lateral motion be perpetually moving and never come to a stop? Assumptions: Perfect vacuum: zero ...
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1answer
630 views

Contact force between two boxes when static frictional force>external force

A question that my friend asked me but I can't figure out why the answer is C. Won't the block not move and net resultant force = -4.525? I haven't learnt about static and kinetic friction and am ...
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3answers
541 views

Static friction free body diagram on a flat plane

Do you include static friction on a free body diagram for a static box on a flat surface? Or do you just include Force of gravity and Normal force? We know when the box is moving there is Frictional ...
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0answers
36 views

When does water decrease or increase friction?

Water often acts as a lubricant e.g. a wet floor or road, but sometimes the reverse happens e.g. putting on wet clothes. I understand that surface tension is involved e.g. microscope slides sticking ...
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5answers
57k 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 is ...
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3answers
2k views

How can a train locomotive generate enough traction to pull all the coaches?

Sorry for posting what may be an obvious question but we just learning about friction at school and my teacher couldn't explain well enough to me and I would appreciate your inputs. Consider the ...
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2answers
501 views

Motion of an object spiraling outwards on a rotating disk with friction

I recently came across the following problem: A spinning disk has an object initially located at radius R. The object is moving with the same angular velocity as the disk (which I will call ω). ...
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4answers
1k views

In which direction does the friction act in a circular motion?

I want to know how a body moves on a circular track. Suppose a car enters a circular path. If I don't turn my steering wheel, then the car would travel in straight line and perpendicular to the radius ...
0
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2answers
44 views

Kinetic friction and Newton's third law

Consider these two cases: 1)An object of mass $m_1$ is on a movable cart of mass $m_2$, coefficient of friction between the object and cart is known.If a force $F$ acts on the object and it's not ...
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2answers
154 views

Frictions in a slowing car

When you apply the brakes to a car and it slows down, there are two kinds of friction and I am getting confused. On the one hand, there is friction between tyres and road. This friction a) Is the ...
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1answer
591 views

Graph explanation for force and friction

Question: A block of mass $m$ is placed on an inclined plane with angle of inclination $\theta$. Let $N$, $f_L$ and $F$ respectively represent the normal reaction, limiting force of friction and the ...
0
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3answers
833 views

Is there such thing as a critical value for the coefficient of friction?

Is it possible for coefficient of friction to be so high that no matter what force is applied to an object, the object will never move? For example, if I have an incline and a box on the incline ...
2
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1answer
158 views

Effect of forces inside a sphere

What would be the effect of applying two parallel forces of the same value at opposite points of the equator inside a sphere? Common sense tells me that it wouldn't move, but it seems that it could ...
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3answers
1k views

Time reversal symmetry in the presence of friction

I was reading a paper on time reversal symmetry, and came across an example of a pendulum swinging in the presence of friction: When we consider the more realistic physical situation of a swinging ...
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0answers
13 views

Does friction torque in speeding up rotation is the same as fiction in speeding down?

I'm trying to calculate moment of inertia of a pulley connected to a shaft mounted on bearing by using free fall method. A load (270 g) is tied to a string and the string is wrapped around pulley. ...
6
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1answer
139 views

What makes a forever spin top special?

What is the difference between a regular spin top and a forever spin top (which spins for far longer than a regular spin top).? The forever spin top is made out of stainless steel. I would like an ...
0
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1answer
68 views

Friction as a cause of motion

Can anyone help me to understand why friction force is not opposing the resultant centripetal force acting on the box and instead being the cause of its existence?
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1answer
60 views

Projectile with linear drag [closed]

A particle with mass $m$ travels with speed $v_0$ and angle $\theta$ compared to the horizontal ground. Air resistance given as $F_R = -m \alpha v$, where $v$ is the particle's speed, is working ...
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3answers
51 views

The direction of friction

How does friction change its direction? What I have learnt till now is that friction opposes the motion of an object. Please explain me the conept of applying friction in free body diagrams when there ...
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3answers
1k views

Materials with directional friction property?

At the macroscopic level a simple metal file or rasp creates a large amount of friction in one direction and a much smaller amount in the opposit direction. Shark skin displays the same properties due ...
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4answers
60 views

If we don't apply force to a body and the friction is zero will the body move?

Imagine a body is kept on a surface with zero friction and no force is applied to the body. So will the body start moving?? I guess it shouldn't according to Newton's first law it will continue to ...
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1answer
483 views

Perturbation Method in Mechanics: Average velocity of a small mass on a vibrating inclined plane [closed]

I've stumbled across this delightful and difficult collection of problems, by Jaan Kalda. The following problem has stumped me. (It's probem 16 on the sheet, which I have provided as a link) http://...
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1answer
450 views

Understanding role of friction in block on block problems

Consider two blocks stacked on top of one another. There is friction between the blocks but there is no friction between the lower block and the table. So the only frictional force that tends to ...
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4answers
5k views

The direction of friction for a car wheel

In this particular example shown the image below (from engineering dynamics - Meriam), I do not figure out why the direction of friction is in direction of the translation of the car? Or I just didn'...
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2answers
296 views

What is the specific source(s) of sliding kinetic friction

In simplistic (K-8) physics classes, it seems to be generally instructed that the friction between two moving surfaces is due to the unevenness of each surface and the microscopic roughness. However, ...
2
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1answer
815 views

Maximum friction force for a wheel to be able to roll [duplicate]

The wheel with mass $M$ and radius $R$ below is free in space (it is not on the ground). A torque $\tau$ is applied to it through an engine. A horizontal force $F = \frac{\tau}{R}$ is also applied to ...
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1answer
308 views

Is there any situation when oil increases friction?

I have read everywhere and tried myself to experience oil smoothening surface interfaces, thereby reducing friction. I was curious if there are instances where oil increases the friction between those ...
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1answer
181 views

About the fluid friction along the wall in pipes

I wonder how can the friction between a fluid and a wall in a cylindrical pipe can be calculated. Is there any theory that I can refer to? I also want to check if there's any relation between the ...
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0answers
60 views

The origin of normal reaction

I want to know what actually is the origin of normal reaction between 2 objects. i have read about normal reaction from several books which generally mention it as a component of contact force which ...
0
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1answer
28 views

A Chain in Equilibrium

My By book says that, for equilibrium Limiting Friction$(f_L)$$=$Weight of hanging chain. But Why??
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1answer
91 views

Derivation of equation of motion for mechanical seismograph

Consider a simple seismograph consisting of a mass $M$ hung from a spring on a rigid framework attached to the earth, as shown in the picture. The motion of the mass is apparently described by the ...
2
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3answers
1k views

Thermodynamics and Newton's second law

Is it correct to say, that the Newton's laws (or a Newtonian system) is reversible if the friction isn't considered (the fact that the time is of second order $\frac{d^2x}{dt^2}$) and an isolated ...
2
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1answer
2k views

Why friction force is force of constraint?

My understanding about constraint force is that it is a force which limits the geometry of particle's motion. For example, situations such as the particle trapped in a track or limited in domain can ...
2
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3answers
212 views

Total force on upper block in two block system

If a block $m$ is placed on another block $M$ and a force $F$ is applied on bolck $M$. Then how many forces are acting on block $m$.(Friction is non zero) The image is taken from this site. Is ...
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1answer
49 views

Why do we consider the viscous force to be tangential?

Is it that since it is a friction force, it needs to be tangential as other friction forces like kinetic friction and static friction forces are?
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2answers
49 views

Can someone explain these circled points…? [closed]

Why is direction of friction in the direction of motion and here it is the platform that moves....the movement is not caused by friction so how is friction doing work? In the second one there is no ...
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2answers
39 views

The reason behind circular motion of vehicles

In all the textbooks and internet resources that I've ever read , most of them explains role if friction in circular motion of an object (let's says a cycle), from the frame of the cyclist i.e. with ...
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2answers
39 views

Friction and Circular Motion

In circular motion, it is said that the friction acts towards the centre of the circular path. But friction opposes tendency of relative motion and since the velocity of the body(in circular motion) ...
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7answers
936 views

Physical Interpretation of an Overdamped Pendulum

Consider a damped pendulum whose equation of motion is given in general by $$m\ddot{x}=-\mu\dot{x}-kx$$ where $\mu,k>0$ Rewrite this equation as $$\ddot{x}+2\gamma\dot{x}+\omega^2x=0,$$ where $...
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0answers
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How does friction cause a spinning top to fall?

I am wondering how friction can create a torque to change the angular momentum and cause a spinning top to tilt, like in the diagram of a close up of the rounded tip of a top while the angular ...
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2answers
99 views

Why does a car which decelerates slowly on a icy road not slip but a car which decelerates quickly does?

Why is it that braking slowly on an icy road is safer than braking quickly. Intuitively it makes sense but what is the logic?