# Questions tagged [friction]

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

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### How to find the equation of motion for a bead of mass $m$ threaded on a circular loop with dynamic friction coefficient $\mu_k$?

I have been working on a particular physics problem but am not sure if I have analyzed it correctly. Here is the problem: "A bead of mass m is threaded on a metal hoop of radius $R$. There is a ...
807 views

### Dissipation and first law of thermodynamics

Consider the following situation: a certain gas is contained in a well-insulated cylinder with a well-insulated piston head. Now, in this case the piston is not frictionless. In order for the piston ...
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### Force of friction in rolling without slipping

Observe this case. We can make two choices regarding the axis of rotation. If we choose an axis of rotation that passes through the center of mass $G$ then the only force that would cause the ball to ...
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### The direction of friction in rolling without slipping [duplicate]

I know there are multiple SE questions talking about this subject but I still don't understand: If I have three balls as seen in the picture, what is the direction of friction on each ball if: No ...
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### Ideal Car in Circular motion [closed]

If i am moving in my car in a circular motion and then i let go of my gas pedal then will the car remain in the circular path forever?i think yes because the frictional force acts only towards the ...
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### Classical mechanical problem consisting of a cylinder rolling on top of a box and the box on top of a smooth surface [closed]

Consider the following classical system. The top surface where the cylinder $m_1$ with radius $R$ rolls is rough enough so that $m_1$ can roll without slipping. The walls sandwiching $m_2$ is also ...
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### What's the most effective direction to apply force in to move an object in an intended direction under gravity and friction? [closed]

Suppose that there is a rigid body on the floor: B ----- I have an intended direction as a vector $\overrightarrow{d}$, pointing left for this example. To ...
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### How do i find the maximum acceleration of a front wheel driven car? [closed]

Whats the maximum acceleration of a 1600kg car? The static friction μ = 0.8. Front wheel drive.
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### Real Pulley and Newton's Third Law

In a real pulley with two masses hanging from either side, the pulley rotates due to a non-zero torque, which I understand is caused by friction on the rope. I understand that if each mass was ...
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### The Cavendish Experiment

I do not get the idea that how does the torsion balance result in a damped oscillation. Two big and small masses separately attract each other. I naively think that after a while big and small masses ...
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### Contradiction regarding friction of a rolling cylinder in an inclined plane

I came upon this while wondering whether the friction of a rolling cylinder on an inclined plane depends on the value of friction coefficient. now, $$f\leqq\upsilon N$$ Again after calculating I ...
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### Motor's work and power against the gravity

Ok, I've read this answer: Why does holding something up cost energy while no work is being done? But more questions pop up. If there is no work being done does that mean that there is also no power ...
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### Why can materials like sandpaper deform hard metals?

I don't have much of a physics background, so my assumptions might be somewhat incorrect. But I've recently seen how sanding tools can be used on materials that are powerful, such as stainless steel. ...
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### How does friction on the front and rear wheels of a car vary? [closed]

Consider a Rear-Wheel Driven car. The questions refer to friction between the wheels and the road. Direction of friction on the front and rear wheels when car accelerates? Is it static or kinetic? ...
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### Why doesn't friction accelerate a ball undergoing rolling?

Consider this situation: A ball is moving forward and undergoing rotation. Assume that it is not slipping. Eventually, the velocity and rate of rotation of the ball decrease, and it comes to a halt. ...
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### Forces on a person in a rotor ride

I am trying to understand all the forces on a person in a rotor ride appearing in the homework problem here. It appear that the the normal force (due to contact between person and rotor's inner ...
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### Direction of static friction in rolling without slipping down an inclined plane

Suppose a wheel is rolling without slipping down an incline. Static friction prevents the impending motion of the wheel relative to the incline. Since the slip is impending in the direction in which ...
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### Friction on atomic scale [closed]

I am getting into friction on an atomic scale. For instance, take two rigid layers of atoms of the kind A that are placed on top of each other, just like putting two boards of wood on top of each ...
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### How (and why) is energy due to friction independent of speed?

Consider a rotating disk and a fixed part that "abrades" something. Under normal conditions the disk and the fixed part should not touch. However, they slightly touch due to misalignment. When the ...
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### Why is horizontal component of reaction force while walking regarded as friction?

The horizontal component of the reaction force responsible for forward movement of person while walking is regarded as frictional force. But when a person pushes the ground backward, the supposed ...
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### Work done by friction on an inclined plane

A rough inclined plane is placed on a cart moving with a constant velocity u on horizontal ground. A block of mass M rests on the incline. Is any work done by force of friction between the block and ...
3k views

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

I have the following question: In the diagram below the mass $m_1$ is moving down the incline . The surface upon which $m_2$ moves is smooth, and the coefficient of kinetic friction between $m_1$ ...
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### Maximum angle that a wheeled body can climb at

I've only recently been introduced to the concept of static vs dynamic friction and I was looking to check my understanding by determining the max angle a wheeled body can climb. In the diagram below ...
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### 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 ...
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### Rolling friction and Sliding friction

I had asked whether the frictional force depends on the surface area in contact but the expets says no... So why does the rolling friction less than that of sliding friction...? Sliding friction is ...
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### Why do people not used walking on flat ice mostly fall backward when trying to? [closed]

It's my experience that most people (including myself) fall backward on their behind when trying to learn to walk forward on flat ice and fall forward when trying to run on it. When walking or running ...
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### Why will the maximum value of static friction act? [closed]

I viewed a similar question but that didn't solve my query.In the shown problem, while solving the equations my teacher just assumes that the static friction will have its maximum value and solves the ...
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### Why doesn't friction depend upon area of contact? [duplicate]

Even though the pressure increases when the area of contact decreases why doesn't friction increase with decrease in area?
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### Friction energy dissipation calculation

In a moving block, a variable force pushes it. Friction is acting against the movement. Below equation specify the amount of energy could be used to give motion: $$E_1 = \int F_T(t) .v(t) .dt$$ ...
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### 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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### Direction of friction force on rotating and slipping sphere

An homogeneous sphere of mass $m$ and radius $r$ with only initial rotation $|\dot\phi(t=0)|= \omega_0$ is placed over an horizontal surface , with initial velocity of translation of the center of ...
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### What does this statement mean?

There was a section of my textbook that mentions this and I can't understand it... Q: Is static electricity caused by friction? A: No. It appears when two dissimilar insulating materials are placed ...
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### Is the squeal a manifestation of the Painleve Paradox?

When a DJ does a rewind (suddenly reverses the direction of the vinyl’s rotation under the needle), a sharp squeal is produced. This squeal is neither simply the music played backwards (as a film ...
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### Why don't we consider internal forces for motion? [duplicate]

I read an example in my physics book and was not satisfied with that. Suppose there is a car initially at rest. If the car accelerates then my book says that it is the friction force only which ...
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### 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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### Friction Between Magnets

I have heard this definition of friction: "Friction is the resistance to motion of one object moving relative to another." So is there any friction between the same poles of 2 magnets? I can feel ...
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### 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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### 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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### Why is Maximum Roll Pressure Not Always at the Plastic-Elastic Boundary?

In the rolling of steel, a sheet of steel is compressed plastically, so that it is thinner upon exit than at entry. This necessitates a change in velocity to maintain mass flow. As a result, certain ...
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### When tyres skid on a dry road, is it because friction is too low or because the rubber is not strong enough?

All other things being equal, a car with wider tyres is less likely to skid on a dry road than one with narrower tyres. As answers on related topics have made clear, the simple formula $F=\mu N$ does ...
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### Damped Oscillation and Period

In my school experiment, I wanted to measure the gravitational constant ($9.81 \ m/s^2$) by using a pendulum. If we take into account the damped oscillation (i.e. friction forces), does that affect ...
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### Direction of friction and normal

We know that friction can be calculated using F=uN Where u is just a constant for two surfaces in contact. So , direction of friction should be the same as of normal but it doesn't happen. Is ...
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### Massless Pulley having friction

I want to ask whether it is (theoretically) possible that there is a pulley with no mass but has friction in it....Why or Why not ? Also will the tension on both sides of it be the same or different (...
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### Do electric cars need friction brakes to stop really fast?

If regenerative braking can't stop an electric car fast enough, can't we actively slow it down by applying a reversed voltage to the DC motor? EDIT: By really fast, I mean in emergency situations ...
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### How is the transition from kinetic to static friction modeled?

There are tons of information about the transition from static friction to kinetic friction but I'm having a little trouble finding information about the converse situation. I need that because I'm ...
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### 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 ...
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### Friction in the case of a inclined plane

Why is the direction of friction on an inclined plane always "up the incline" when a body goes up or down the plane with pure rolling motion?
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### What will happen to a ball kept on a frictionless inclined plane?

I was wondering about this question since I learned about rolling motion in the chapter on rotational mechanics. I was unable to come to a solid conclusion due to the reasons mentioned below. The ...