# Questions tagged [friction]

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

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### Couple or torque

In the solution of Problem 527, over here, A homogeneous cylinder 3 m in diameter and weighing 30 kN is resting on two inclined planes as shown in Fig. P-527. If the angle of friction is 15° for ...
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### Sliding to Rolling

In a problem where a sphere is initially sliding and then begins to roll after having travelled some distance. The thing that confused me is that the work done by friction on the sphere is not simply ...
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### Does ABS increase the breaking distance of a car? [closed]

Question: Can an ABS (Anti-lock Braking System) instead of decreasing the breaking distance actually increase it? If yes, is this its general behaviour, or only in specific circumstances? Wikipedia ...
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### Tire pressure physics

I understand that with less tire pressure you get more surface area on the pavement and more friction which gives more rolling resistance, but does having less air mean that there’s more weight per ...
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### Deriving equations of motion using Lagrangian formalism for inverted pendulum on a cart with friction between pendulum and pin

I know this is a problem with plenty of examples and solutions but I can't find one where the friction between pendulum and pin (I know it's negligible) is taken into account. My main question is if ...
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### Rotating object on table: from sliding to rolling

A object which is rotating around a horizontal axis is placed on a surface, and starts sliding (with kinetic friction). After some time, it starts rolling without sliding through the table. The goal ...
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### Work done by non-conservative force like friction

I have two questions: Q1 Why is work done by friction path dependent? Let us say that there are two points A and B that are vertically at a distance 'd' apart from each other. If I take an object ...
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### Can I know if an object will slip or will accelerate forward when it is pushed by a force that exceeds the maximum force of static friction?

If we push a trash can, it will not move until we exceed the maximum force of static friction, but when we exceed the maximum force of friction, will the can slip or accelerate forward?
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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,...
364 views

### 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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### 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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### 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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### 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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### 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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### 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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### 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 ...