# Questions tagged [friction]

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

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### Does friction always oppose motion?

Recently I had the following misconceptions: Static friction always opposes the motion of body. The force of friction cannot initiate motion in a body. Now I came to know that my understanding was ...
130 views

### What force stops a car?

I've been doing physics problems regarding cars for a while. I understand that there is a static friction (which appears when the wheel is rolling) and kinetic friction (which appears when the wheel ...
46 views

### Braking systems on cars

I thought of a maths problem for myself to solve, as it seemed like a good problem to try to get my head around. My issue is that I got stuck at the first hurdle. I was reading up about the braking ...
182 views

### Why do office chairs rotate when pushed/pulled out?

A common source of frustration when I'm at work is the fact that my rolling office chair's wheels rotate whenever I push it forward or backward from my desk, which can cause it to bump my computer ...
76 views

### Why does a ball keep rolling?

When a rigid ball rolls on a plane with no other forces, it is known that no friction applies and the ball keeps rolling. I was asked if this $F_{\text{friction}}=0\,$ can be derived from the usual ...
62 views

### Can a spinning ball bounce off the floor without slipping?

Suppose a ball is dropped vertically downward, but it also given some spin along a horizontal axis. Then when the ball bounces, it will presumably pick up some horizontal velocity. Is it possible for ...
58 views

### 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 ...
58 views

### In Feynman lecture Vol1. chapter12 about friction, $F = μN$ will fail because of the excessive heat generated. Why is that?

$F = μN$ will fail because of the excessive heat generated if the normal force or the speed of motion gets too big. Why is that? "$F = μN$, where μ is called the coefficient of friction (Fig. 12-1)....
11 views

### In Feynman lecture vol1，chapter12 friction between two wet glasses, is there any atmospheric pressure related during the process?

In Feynman lecture vol1，chapter12 friction between two wet glasses, is there any atmospheric pressure related during the process? Does the water between two glasses make use of atmosphere pressure? Or ...
49 views

### what does Feynman lecture 12 friction “outgas the materials in a vacuum” mean? What is the purpose of doing that？

what does Feynman lecture 12 friction “outgas the materials in a vacuum” mean? Does it mean that the experiment is carried out in vacuum? What is the purpose of doing that？ “It was pointed out above ...
151 views

### Opening a bottle cap

How exactly is a bottle cap opened/closed? To open/close one, it needs to be rotated and simultaneously translated upwards/downwards for it to move up/down its thread and not be translated right or ...
175 views

### How can a body have constant velocity when net force on it is zero?

Considering Friction is here.. How can a body move with uniform velocity, to move with uniform velocity it should have acceleration equal to zero, for this suppose a body on which a force F is acting ...
125 views

### What would be the optimal diameter of gold grains if you want to fill a pool with them and swim in it?

I was wondering, if I were to fill a pool with gold/gold dust, what would be the optimal diameter of the grains to minimalize the friction to a point at which you would be able to swim in it ((and if ...
72 views

### Can there be instantaneous change in force (friction)?

When an object is moving on a rough surface with only frictional force acting on it, there will be some kinetic friction on it which is constant until object comes to rest. The moment it stops, ...
95 views

### Cracking of pages

I have noticed that after using a book for some time, a few pages develop small cracks on them. What is the science behind it and can it really damage a book? Basically, something like this: And, if ...
13 views

### What is the surface roughness of glass-filled Nylon?

I need to calculate the water pressure loss in a pipe made of glass-filled nylon. The pipe is used for irrigation/gardening. I planned to use moody chart to find the friction factor, but I can't find ...
176 views

### What would be the minimum height for a complete lap?

An empty ball, of mass $m$ and moment of inertia $I = \frac{2}{3}m.r^{2}$, is rolling across the path shown below: there is friction $f_{r}$ from A to C . $r$ is the radius of the ball, and $R$ ...
54 views

### Effect of air resistance of the period of a pendulum [duplicate]

Does air resistance increase or decrease the period of a simple pendulum?
34 views

### Calculate the kinetic friction velocity vector from the kinetic friction force in a simulation

I am doing (programming) a simple kinematic 2D simulation on blocks. The idea is that the block will have a force applied. 1) From the force and mass I calculate the the acceleration vector (will ...
42 views

### Why is it easier to catch mosquitoes with your hand when your hand is wet?

Recently I've noticed that it's significantly easier for me to catch a mosquito with my hand if my hand is very wet (e.g. from having washed my hands and not yet dried them, or from being in the ...
107 views

### How do knife blades become dull?

Knives are normally used to cut softer objects. So the edge of the knifes blade is harder than the substance it cuts through. A blades geometry is more complex, but let's simplify it to the blade ...
24 views

### Relation between rain, time and terrains

I would like to understand whether an approximate relation between the rain and the physical properties of a particular terrain (composed of a specific material such as asphalt or clay or grass or ...
54 views

Can there be friction between two contracting surfaces even if they do not slide over each other?
54 views

### Is friction an emergent phenomenon?

The microscopic origin of the frictional forces is due to contact between irregularities of the surfaces as seen here [1]. Electromagnetic interactions are the fundamental forces responsible for ...
11k views

### What happens to the coefficient of friction as the normal force increases?

Does the frictional force increase as the normal force increases, or does the coefficient of friction get smaller in value?
130 views

### Why does Friction act Parallel to the Surface (Microscopic Level)?

If we assume an object (blue layer) sliding towards the right across a surface (black layer). According to Newton's 3rd Law, the frictional force would act to the left (resisting the object's relative ...
13 views

### Friction and Electric Forces [duplicate]

As I understand, friction arises from electromagnetic forces. Electric fields, at least static ones, exert conservative forces. So how is it that friction is non-conservative?
65 views

### Pure rolling and friction

If I launch a rigid cylinder (or sphere, etc.) to the surface which has a coefficient of kinetic friction $\mu_k$ and static friction $\mu_s$ with some initial velocity $v$ I think it will decelerate ...
78 views

### Friction when walking

To meet a U.S. Postal Service requirement, employees’ footwear must have a coefficient of static friction of 0.5 or more on a specified tile surface. A typical athletic shoe has a coefficient of ...
38 views

### Problem regarding friction

I require a clarification on some steps in the solution of the following problem. Problem: The coefficient of static friction between two blocks shown in figure is μ and the table is smooth.What ...
26 views

### Calculating Rolling Friction in a Lab

What would I have to measure to determine the rolling friction of a model car? Currently, I have the horizontal pulling force that the lab procedure calls for on the car, and enough data to make a ...
70 views

### How long would “artificial gravity” remain on an O'Neill cylinder without power? [closed]

An O'Neill Cylinder (as defined by O'Neill, per Wikipedia) has two cylinders which are both "5 miles (8.0 km) in diameter and 20 miles (32 km) long, connected at each end by a rod via a bearing system"...
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### Rubber-Rubber friction

We all know rubber is known to have a high friction coefficient, and it's quite difficult to drag a block of it across a surface. What happens when two blocks of flexible rubber are dragged against ...
29 views

### Finding acceleration of a stacked box system, when they are not relative [closed]

Two boxes are stacked, box $A$ is placed on a horizontal surface with no friction, box $B$ is placed on box $A$ with unknown coefficient friction between the two. Box $A$ does not slide relative to ...
37 views

### How can a rope's tension be at a maximum as a body is about to move up a slope in the rope's direction? [closed]

Note: I do NOT need this exercise's answer. I have no problem working the math out and noticing the truth of my title. A box of mass 0.5 kg is placed on a plane which is inclined at an angle of 40 ...
326 views

### Friction in pulleys

The moment equation of a pulley with a rope applying tension on both sides is as follows: $$I\alpha = f + T_1R - T_2R$$ ( $I$ - moment of inertia; $\alpha$ - angular acceleration; $f$ - friction ...
242 views

### Friction while Rolling Without Slipping

This is an excerpt from an elementary Physics textbook ("Fundamentals of Physics" by Halliday), which describes what happens when a wheel that is "rolling without slippging" doesn't have a constant ...
68 views

### Problem with Impure Rolling [closed]

Can someone explain what happens in the below situation Looking at it from the planks frame of reference: The cylinder Velocity= 20(-i) Net friction force on cylinder f=2umg(i) (here u=1/2) ...
35 views

### Factors effecting the time period of Euler's disk [closed]

I wish to carry out research on the factors effecting the time period of a spinning Euler's disk. Do factors like friction coefficient of the base or concavity of the base effect the disk? If not, ...
54 views

### Turbulent flow in a pipe - how to compute the friction coefficient $\lambda$

Consider a pipe of diameter $D = 0.01$ m and Length $L = 1.0$ m represented in the figure underneath. At the in- and outlet, the pipe cross-section converges, respectively diverges smoothly. We will ...
100 views

### Understanding the notion of lose or win of angular momentum in accretion disk

Here is below a slide of one of my lecture in planetology : I understand well the fact that ring A will be slow down by friction with ring B since ring B is rotating slower and the inverse process (...
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### What are the forces acting on this car?

i found a cool website that explains sort of like the forces acting on the car and they seem to explain the process behind it. the website gives a free body diagram but the problem is that it doesn't ...
43 views

### How does different shuffleboard powder affect the disks' speed

I do know there is friction and surface tension involved here but am not sure on how exactly does different kinds of shuffleboard powder affect the disks' speed. So taking into the account the ...
900 views

### Does rolling friction increase speed of a wheel?

I know there are a lot of questions about rolling friction, but I couldn't find any that addressed my specific problem. Note the following picture where the wheel rotates clockwise. The rolling ...
53 views

### Explaining friction using Hamiltonian mechanics

I have heard the opinion that it is a good assumption that microscopically all forces are actually conservative so in principle all classical mechanics problems could be solved using Lagrangian / ...
4k views

### Does Mass affect Speed of a Sliding Object With friction?

Sorry if this has been already asked, but I've been looking around google for a while and couldn't find an answer suitable. I'm a beginning physics student so pardon the dumb question. Let's say we ...
1k views

### Why we can't write in air? [closed]

Why we always require a surface to write something? Why we can't write in air? I think that it is due to friction but I am not sure about it. Edit As per helpful comments and responses, I think ...
94 views

### Is friction enabling relative motion between bodies in contact?

If the surface object B is placed on is frictionless, on applying a force F on object A, friction will act on object A opposite to the direction of the force applied (opposite to the direction of its ...