# Questions tagged [friction]

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

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### Fing static friction of rolling without slipping in harmonic oscillators

My Problem I found a question online and wasn't able to solve it. I ask for guidance and/or an explanation of how should I "get rid" of the static friction in the equations I wrote? (I will ...
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### Direction of friction of a rotating ring/disk

I'm trying to understand friction but I'm getting a bit confused... If I have a ring rotating on the ground around its COM what is the direction of the friction? If I have the same ring, but this time ...
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### What acts first, friction or tension, if one pulls a block on a rough surface attached to a wall using a string? [closed]

Consider a rigid block placed on a rough surface attached to a wall using a massless string where $\mu=0.5,\ m_{\text{block}}=1$kg. Now, if the block is pulled with a force of $20N$, what acts first, ...
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### If I move a negative charge towards positive one on a rough surface then where does its potential energy go?

Suppose I have a positive charge and a negative charge at a distance on a rough table. The friction of the table overcomes the electrostatic force between them. So, they are stationary. Now, I push ...
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### Stacked bodies, no applied forces, internal forces accelerate the whole system [closed]

A block P of mass $m_{1}$ in on a frictionless horizontal plane and a block Q of mass $m_{2}$ is always on top of P. Initially P and Q are at rest. At time t=0, an initial speed $v_{0}$ is given to P ...
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### Net Force on a System [closed]

In the figure given below is a system of a mass M ,a pulley and 2 masses of mass m. Now there is friction between bodies A and C and B and C. A force ($F$) is applied in such a way that body C is a ...
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### Why do flat-plate friction studies only consider half the plate?

I'm trying to learn friction (only - nothing else - just skin friction) on a surface as it moves through water. I'm hoping to find a working formula, including all necessary units, in terms of wetted ...
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### Friction on a wire (angle of repose) [closed]

A wire is molded into a shape in vertical plane as shown. The equation is given by $y=0.5\sin 2x$. A bead B can slide on the wire.The coefficient of friction between bead B and wire is $0.5$. The ...
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### Work-energy theorem and the frictional force

During my attempt of fully grasping the work energy theorem, I came across this written in my textbook: The frictional force, which we represented as a constant force is in reality quite complicated, ...
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### Problem with friction in circular motion [closed]

I can't seem to understand what would be the direction of friction in the case of uniform and non-uniform circular motion. Can someone please help?
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### Expansion in spring with two masses at its end [closed]

Two solid spheres (mass and radius may be considered same or different by the one who answers) are connected by a spring with spring constant $k$ and the entire setup is on a surface with coefficient ...
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### Pressing a mass against a spring on a table with friction

Suppose I have a mass $m$ kept on a horizontal table with coefficients of friction $\mu_{s}$ (static) and $\mu_{k}$ (dynamic/kinetic). And suppose I have a spring with spring constant $k$ which is ...
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### Is friction different when viewed from a non-inertial frame?

I encountered this diagram when reading an explanation about why the front wheels of cars lift up when they accelerate. The diagram is in the reference frame of the car, so that there is a fictitious ...
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### In which direction will the friction act?

Suppose a block of mass $1$ kg is kept on a rough horizontal surface. Let the friction coefficient be $0.2$. Now let's say, I apply a force of $1$N in the east direction. Friction will act in the ...
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### Why does a bike skids on the sand?

Whats the theory behind bike skidding on the sand? Is it related to friction and if then why it skids. Is that the sand has more friction if so then pedaling should be difficult rather than skidding.
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### What forces are there against the motion of walking or running?

When we walk or run, are there any forces that counteract the static friction between our feet and the ground? I can’t seem to think of any, but if not, why is it that we still need to push on the ...
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### The curl of a friction force being zero

Consider the resistive force modelled by the function $\vec{F} = -b\vec{v}(t)$. The curl of this function, $\nabla \times \vec{F}$, is [\frac{\partial}{\partial y} (\frac{dz}{dt}) - \frac{\partial}{\...
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### Moving with constant velocity in presence of net force

If I neglect air resistance is it possible that I can walk with constant velocity? Suppose that I take equal steps of equal length every second and therefore my velocity doesn't change. That means ...
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### Calculate the acceleration of a superman in running shoes [closed]

The friction coefficient between an athlete's shoes and the ground is $0.90$. Suppose a superman wears these shoes and races for $50 m$. There is no upper limit on his capacity of running at high ...
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### Worked Example - Classical Mechanics by David Morin

Problem: A rope wraps an angle θ around a pole. You grab one end and pull with a tension $T_0$ . The other end is attached to a large object, say, a boat. If the coefficient of static friction ...
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### Physics of a coin on a turn table

Suppose a coin is placed on a turn table which is then rotated. The coin initially rotates along with the disk and may fly off eventually. My question is, why is static friction acting radially inward ...
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### Why does the glass move?

I have observed at my home that when there is a small puddle of water on a glass table and an inverted steel glass is kept on that puddle of water, the glass starts moving on its own after some time. ...
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### Work of friction on rolling objects

In many cases when there is friction acting on a body which is rolling without slipping ( for eg : a body rolling down a inclined plane ), We say, that the work done by the friction is zero as the ...
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### What happens with diamond on atomic scale when we simply touch it?

We all know that diamond has very strong covalent bonds that require a lot of energy to break. We can destroy it by burning it, but what happens when we touch or rub it with a soft material? How long ...
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### Torque on a block on an inclined plane

When a block is stationary on an inclined plane, the frictional force on the base of the block has a torque about the center of gravity of the block. However, the block does not rotate. Which force ...
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### Objects rolling down inclined plane at different speeds

Consider the case of objects rolling down an inclined plane at different speeds depending on their moment of inertia. Some basic equations are shown in this screenshot from Michel van Biezen. He is ...
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### Why can't we take the surface as part of a system when conserving linear momentum?

In a problem I'm facing, friction acts on the system that I wish to apply conservation of linear momentum. Why can't I take the surface as a part of system and conserve momentum? As the surface is ...
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### Are objects at high speeds subject to friction (in described fashion)?

https://www.youtube.com/watch?v=1NnyVc8r2SM In this video quicksilver moves plastic bullet's with his finger from a different time reference. Needless to say, if bullets were in contact with an ...
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### Where does the equivalent friction act on a block sliding on an incline?

If a block is sliding down an incline it means the Normal force is acting at a point $x$ distance from the middle of the bottom of the base to produce an anti-torque to keep the body in rotational ...
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### What lies between “perfectly smooth” and “perfectly rough”?

In elastic collisions of spheres, there are two approximations that can be made: Either they are perfectly smooth, and you ignore the rotation component, or they are perfectly rough and the rotation ...
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### Why is heat energy dissipation in two intervals frame dependent?

The question asks for heat produced in the given specific conditions. It seems like an application of the work-energy theorem with friction doing work on the block and dissipating the heat in the ...
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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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### 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 ...