Questions tagged [friction]

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

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How does the static friction $\vec{F_{1,2}}$ and $\vec{F_{2,1}}$ generate here?

How does the static friction $\vec{F_{1,2}}$ and $\vec{F_{2,1}}$ generate here? I am confusing with $\vec{F_{1,2}}$ and $\vec{F_{2,1}}$ My understanding from the video:- If we push the block (2) with ...
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Frictional Brachistochrone Solution [on hold]

Using the functional $$T[y] = \int_a^b \sqrt{\frac{1+y'^2}{2g(y-\mu x)}}dx,$$ I have found that the solution to the frictional brachistochrone is $$y = \frac{1}{2}k^2[(t-\sin(t))+\mu(1-\cos(t)]$$ $$...
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Why consider only $x$ component of accelerating block pulled by cord at an angle?

A $5 \, \text{kg}$ block is pulled along a horizontal frictionless floor by a cord that exerts a force $F=12 \, \text{N}$ at an angle $\theta = 25 \, \text{deg}$ above horizontal. What is acceleration ...
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Question related to maximum static friction and minimum $\mu_s$

I think I have the right formulas the answer the following question, but there is something conceptual that is throwing me off (see end of question). A body with mass $m$ is located on a slope with ...
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How do I know that $\mu_k$ independent of velocity and the area of contact?

Doubts:- Although he is stating that till now there is no effective model to explain kinetic friction. (1)Why Kinetic friction is independent of the contact area of the body with the surface? (2)Why ...
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42 views

Inclined plane with friction and a spring

I am given a body with a mass of 1 kg that slides at a constant speed down an inclined plane with an angle of 30 degrees. At the end of the incline there is a spring with a spring constant of 500 N/m. ...
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Is it possible to model a locomotive capable of going 0-60 in 60 secs with $\sum F=F_{engine}+\mu_{rolling}mgv$?

The problem of just considering engine force and rolling friction $$\sum F=ma=F_{engine}+\mu_{rolling}mgv$$ is that when you solve for velocity like $$\dot v=\frac Fm-\mu gv$$ with initial ...
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Will friction on tyres due to road still act if the vehicle is moving with constant velocity?

A car moves with the help of friction from ground...while analyzing a car moving with constant velocity..should one consider the frictional force acting at the contact point of road and wheel? If ...
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Static friction in a slope and two boxes problem

The context: Calculate the string tension in the situation where two boxes are stacked on a slope and moving with uniform velocity, given that the kinetic friction coefficient between the heavier (...
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Unequal forces acting on two blocks connected by a string [closed]

Two blocks A and B are separated by some distance and tied by a string as shown in the figure. Find the tension in the string. I can see that maximum value $f_1$ can attain is $7 N$ and the maximum ...
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Vertical component of friction

If we have a car of mass $m$ sliding around a banked curve of angle $\phi$ with some coefficent of friction ${\mu}$, then the normal force will be $$Ncos\phi= mg + {\mu}F_{g}\sin\phi$$ But this ...
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Help with the problem of moving two fingers along a yardstick

The following problem is taken from an MIT homework assignment: Hold a yardstick horizontally on your index fingers and slide your fingers together smoothly. The stick slides first on one finger, ...
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Friction at high speeds

I am reading a book which mentions that frictional force is not exactly proportional to the normal force at high speeds. Quoting: Once the bodies slip on each other frictional force is, $kN$. This ...
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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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How does friction product heat?

Suppose there are two similar particle-like objects attempting to "bump" against each other to create friction, they are prevented from colliding against one another due to either electrostatic ...
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Is it possible to find $\mathbf{v}$ explicitly when $\mathbf{F}$ varies with $\mathbf{v}$?

I have the following problem (NO, this is not to ask for a solution to this problem). A block is placed on a plane inclined at an angle $\theta$. The coefficient of friction between the block and ...
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Effect of Particle Size on Angle of Repose for Sand

I have been doing research into how the size of granular material affects the angle of repose. There have been several conflicting results on this topic. Several papers cite that the angle of repose ...
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Bounding the height of the toppling force on an object

On the above question, for the upper bound I took moments about the right bottom corner, resulting in the upper bound: $$ H_{UB} = mg\frac{b}{2F} $$ For the lower bound, I took moments about the COG: $...
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Conservation of energy with friction on a pool ball

I have a problem where I am given the mass $m$, radius $r$ and friction $\mu$ between a pool ball and table. The ball is not initially moving but at $t=0$ is struck by an impulse $$p=\int_{-\epsilon}^...
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Laws of motion (friction on rough inclined plane)

For equilibrium of a body on an inclined plane of inclination 45°. The coefficient of static friction will be 1) greater than one. Why? My question is why do we use greater than sign instead of ...
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What frequency is the scratching of finger nails on a blackboard?

This is the frequency/intensity that sets my teeth on edge. Does anybody know what frequency (roughly) it is? I am guessing it is near the top of normal human hearing, 20kHZ, but I'm not sure if ...
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Work done by static friction in Rolling

In rolling without slipping, I understand that the velocity of the point where static friction with the ground is 0, and therefore static friction cannot do work. However, from newtons laws, an object ...
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Discontinuity in fluid friction as a function of Reynolds number

I have observed a discontinuity in the Fanning friction factor chart, at around Reynold's number of 2000. I know that this is the region where laminar flow changes to turbulent flow, but a ...
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Does the force of friction helps us to accelerate while running? [closed]

The question is to find the correct statement: Cause of increase in kinetic energy while running is due to the work done by friction force without which he cannot run. OR Cause of increase in kinetic ...
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Why does friction not accelerate a wheel?

It seems like a silly question because this defies common sense, but it appears that friction is supposed to accelerate a wheel (not attached to anything). We can derive from Newton's laws that $\...
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Are constraint relations valid on friction

I was doing a question in Newton's laws of motion where I came across this question . The question said there was same frictional coefficient between all surfaces and there is no acceleration of the ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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)....
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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 ...
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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 ...
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1answer
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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 ...
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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 ...
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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 ...
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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, ...
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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 ...
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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 ...
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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 $R$ ...
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Effect of air resistance of the period of a pendulum [duplicate]

Does air resistance increase or decrease the period of a simple pendulum?
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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 ...
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Forces acting on an aircraft during landing

I am currently busy with a project which involves the design of a landing skid for an unmanned aerial vehicle. I am currently underway with calculating the forces which will act in on the landing skid ...
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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 ...
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Calculating rolling friction of a toy car's wheels, not on an incline

I'm dealing with a small toy car consisting of a bottle that has a small hole in the back, covered by a thumb tack. The bottle is filled with pressurized air then the thumb tack is released, releasing ...
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Directions of static & kinetic friction?

Static friction : Static friction opposes relative motion between two surfaces. The car is moving at some tangential velocity relative to the road. Thus, static friction should act in the opposite ...
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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 ...