Questions tagged [friction]

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

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2answers
144 views

Adhesion vs Static Friction

I feel like this question should have a simple answer, but I haven't been able to find one anywhere. I hope someone can help: In short, my question is why the force of static friction is so much ...
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Can a pair of frictional force have positive work?

My teacher told me that friction can have positive work which is true. But he told that a pair of friction forces can never have positive work. I am not able to think the reason for this statement. ...
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Is it possible to have a coefficent of friction of zero?

I know that friction is determined by the equation $$F_f = \mu_fF_n ,$$ so technically if the normal force is $0$ then the force of friction will also be zero, but my question here is whether or not ...
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How is damping force related to frictional force?

I have a problem and I want to determine the friction coefficient using diffential equations i.e. solving the equation (this is from a Under-damped Oscillator) $$ m\ddot x+c\dot x+kx=0. $$ Suppose I ...
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Friction and Work in Inertial Reference Frames [duplicate]

Say a train is moving in the positive $x$-direction at 100 meters per second with respect to the ground frame. Now let's say someone is pushing a large box in one of the cars of that train in the ...
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Predicting Rotation vs Sliding Forwards when Pushing an Object

Suppose there is a cuboid object sitting on a table, and a force is then applied to it. This figure shows the top-down view: I am curious to understand how the object will move due to this force, ...
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How can the friction force equals to the net force in this momentum question?

Question- from https://www.physicsclassroom.com/calcpad/momentum/prob29.cfm A physics student hurls a $315-g$ ball directly into a $3.54-kg$ box which is at rest on a table top. The baseball strikes ...
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Confusion about conservation of linear momentum in a bike

A bike is moving with some velocity.There is some frictional force between the wheels of bike and ground.Now you apply brakes and the bike stops after some time.Brakes apply a force say F on wheels ...
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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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If you set crates of different masses to the same initial velocity, which one will stop first and which one will have the greater displacement? [closed]

If you set two crates of different masses to the same initial velocity, which one will take the longest amount of time to come to a stop? Which one will travel the longest distance? Which one will ...
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Why do bikes hardly ever skid while braking with the front wheel?

When abruptly braking with the rear wheel on a bike, it tends to skid pretty easily. Doing the same with the front wheel is a very different experience. Instead of skidding, the bike lifts the rear ...
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1answer
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How much clamping pressure would it take to hold up the weight of a human?

I don't know anything about physics. This question comes from an argument I had with a friend. Basically my question is this: Is it possible for a human to hold themselves up only by clamping their ...
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Mathematical Mechanics - Friction Question (weight is laid upon an inclined plane)

A weight W is laid upon a rough plane [µ=1/(sqrrt3)] inclined at 45 degrees to the horizon. It is connected by a string passing through a smooth ring A, at the top of the plane, with a weight P ...
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How can static friction depend on the normal force, but be directed orthogonal to it?

According to my understanding: two orthogonal forces aren't related and two orthogonal vectors don't affect each other the force of static friction $F_s$ depends on the normal force $F_n$, so $$F_s = ...
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Does static friction apply when an object stops for a very small amount of time?

It is my understanding that static friction between two surfaces arises at least partly due to inter-molecular forces, e.g. Van der Vaals forces. The question: Consider this scenario: If I push a box,...
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Sharpening Scissors with aluminium foil

There are lots of websites 1, 2,3 that claim you can sharpen scissors by cutting aluminium foil. Does this work? What would be the cause of this?
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Rolling friction - neglection of reaction force on the opposite side

This is a picture taken from wikipedia. Here the rolling friction is explained. W is the weight, F is the driving force( neglecting friction in the bearing etc,) r is the radius of the wheel, R is ...
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What is the reaction force if i push my leg downward in deep space or on a friction less surface? [closed]

As per newtons law,for every action there is an equal and opposite reaction. Consider first situation,if i exert a force on a friction less surface,what is the reaction force? What will be the ...
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The radius of a body in circular motion

If the kinetic energy of an object in circular motion due to a gravitational force is given by: $$E_{kinetic} = \frac{GM_{object}M_{planet}}{2X_{radius}},$$ then why does radius decrease when ...
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Is the mechanical power output of a car constant?

According to my textbook. The mechanical power output of a car is constant. My reasoning tells me otherwise though. According to a lot of pages on this forum related to the driving force of a car. ...
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1answer
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Force required to move bar at one end

A uniform bar of length $L$ and weight $W$ rests on a level floor so that there is a uniform contact pressure between floor and bar. A horizontal force $P$ is applied at one end, normal to the bar. If ...
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Elementary physics question related to banking on roads

I am studying 12th grade physics. I encountered this concept while studying circular motion and frictional force. You can find the relevant equations here Friction on roads While practicing the ...
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1answer
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Is friction affected by gravity?

Some people said that moving a car on the moon would make the tires spin a bit more compared to Earth's. But then I started thinking that if static friction and gravity are perpendicular to each other,...
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1answer
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Why doesn’t a ball “roll” straight down the wall?

I conducted a physics experiment today. I simply held up a small ball against the wall, and let go. I was expecting the ball to exhibit some rolling motion of some sort due to friction, but to my ...
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1answer
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The path of a disk/cylinder with translation and rotation [closed]

The conditions: We have a regular disc of mass $\mathrm{M}$ and radius $\mathrm{R}$. It is placed on a horizontal plane with friction (which is constant throughout). It is then given an initial ...
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1answer
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Motorcycle wall of death: what diameter should the enclosure be so that the cyclists can travel at maximum speed? [closed]

You are asked to build a country fair version of an old classic motocycle stunt in which the riders start inside a circular enclosure with vertical walls about 4.90 meters high. Around the top of this ...
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Why do lighter pendulums come to rest faster than heavier ones?

I've been reading this website, which stated: All pendulums eventually come to rest with the lighter ones coming to rest faster. I have been taught the mass of a pendulum does not affect its ...
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Why does water hold up between the teeth of my comb?

Image for reference: As can be seen in the above image, whenever my comb comes in contact with water, a little of it is trapped between the teeth. This happens whether I dip it in still water or ...
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Why do we assume the coefficient of static friction is maximum in problems involved with rolling objects on inclined planes?

The maximum force of static friction between two surfaces is roughly proportional to the magnitude of the normal force $N$ pressing the two surfaces together. In many problems involving rolling ...
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4answers
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Why is $mg = bv$ and not $mg = -bv$?

I was given two formulas, $$F_D = -bv $$ $$F_D = -bv^2 $$ and was told that at terminal velocity, $$v = \frac{mg}{b} $$ which implies that $$mg = bv$$ $$mg + (-bv)=0$$ $$mg + F_D = 0$$ From ...
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1answer
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$μ = \tan\theta$ - Why? It makes sense mathematically, but if it's based on the materials how does that work?

We were presented with a problem in physics today in which we calculated that the coefficient of static friction is equal to the tangent of an angle This is on a ramp using the laws of friction. My ...
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1answer
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Friction between two blocks on top of each other

I am a little bit confused to the concept of friction between two blocks on top of each other. there could be two situations: the first situation is when all surfaces are frictionless including that ...
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Special cases in friction [closed]

Imagine that 2 objects are stacked. The friction between the objects is higher than the friction between the bottom object and the ground. Is it possible for the top object to be pushed hard enough to ...
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108 views

Dynamics of a sphere in a horizontal plane driven by a force

I'm studying the dynamics of a sphere in a horizontal plane driven by a force. The situation is the following: I have a stationary sphere of mass $m$ and radius $r$ in a pool table whose lining has ...
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1answer
27 views

Dynamic friction

In my house, we are debating whether when you scrub the floor it is easier or more difficult to drag a piece of furniture. My floor is made of marble, who's right?
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Displacement using work energy principle

How do you use the work energy principle to find the displacement of an object. With of course the mass, speed and friction forces given?
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132 views

rolling friction of a solid sphere

This may be a very rudimentary question. I have two spheres on a physics simulator and I need to define various parameters including rolling friction, spinning friction, inertia, color etc. I was ...
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3answers
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How long does a coin take to slide off a turntable?

So I was helping my daughter prepare for a AP physics test. I studied Physics at university many many years ago and always assume I'll be able to figure out any reasonable question about mechanics. I ...
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1answer
219 views

Maxwell's wheel and friction

We experimented with the Maxwell's wheel today and at the end we were asked about why does this apparatus stop since there is conservation of energy. I did some research and apparently there is a type ...
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204 views

Work done by friction on a body which is rolling on an inclined plane [closed]

Why is the work done by friction zero during translational motion but nonzero when the body is rolling on an inclined plane?
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Basic question on friction

Consider the whole system initially at rest.Suppose there is friction between the blocks, but not between the lower block and the floor. Suppose I apply a Force F to the left over M, with F greater ...
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1answer
51 views

Damped oscillations and generalized friction

I'm reading damped oscillations from the book Classical Mechanics by Landau and Lifshitz, quoting from the text - "There exists, however a class of problems where motion in medium can be ...
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How friction works? [duplicate]

I learned that friction comes from the tiny crashes between the small bumps of uneven surface of each object. And I could make a rough guess about why heat is produced when two objects are rubbed ...
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1answer
466 views

How does one mathematically derive the damping coefficient of a theoretical viscous dashpot?

I am very well aware of how to get the damping coefficient experimentally by observing a system in action. Given the dimensions and fluid properties of a theoretical viscous fluid dashpot, how does ...
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1answer
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Dependency of kinetic friction [duplicate]

1.Why kinetic friction doesn't depend on speed of object? Also explain why static friction > kinetic friction > rolling friction? 2.when we keep a book on a table , the table is said to exert a ...
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Rolling friction and motion [duplicate]

The frictional force in a motion of a rolling body is along the direction of motion. Then what stops the motion of a rolling body?
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164 views

Finding the frictional coefficient

This is going to be very long question. A 1 kg block situated on a rough incline is connected to a spring constant 100Nm as shown in fig. The block is released from rest with the spring in the ...
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When you have engine at idle and turn your car, where does the kinetic energy go?

When you turn the front wheels to the right for example, your car will tend to continue in its original forward direction. However, there is friction between the wheel and the ground that prevents it ...
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How far does a teflon ball roll on a very even surface? [closed]

As teflon has a minimal frictional coefficient of about 0.04, how far does a ball made of teflon roll on a even surface in comparison to another ball (made of wood or iron, for example), when pushed ...
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Damping in a stick-slip model

Usually the spring/block stick-slip models also include a damper. eg: https://nptel.ac.in/courses/112102015/10 I don't really understand the purpose of the damper. What does it represent? Also, ...