Questions tagged [friction]

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

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What work, and why, is being done on this system of two rotating circular disks

A uniform circular disc with mass $m_1$ and radius $R_1$ is fixed at its midpoint and rotates at angular velocity $w_1$. Another uniform circular disc with mass $m_2$ and radius $r_2$ is carefully ...
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Velocity and related frictional forces

I will illustrate my question using a simple example. Lets imagine the folowing situation: a big surface, a book on this surface and another smaller book located on the first one. There is friction ...
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Friction during ball backspin and overspin

I already know sliding friction of ball on a flat table and rolling resistance of it. How do I know coefficient of friction value when the ball has backspin with some angular velocity $\omega$? And ...
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Stopping a spinning object with a flexible gripper

I would like to know how deformation of the contact surface affects friction of a spinning object. In the image below I have a 2D problem of a spinning circle with two elastic "fingers" pinching it ...
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Work done in equilibrium positions

I am confused in work done against friction. Let $F$ be the friction when a big stone is pushed by person on ground and $T$ be the component of force applied by a person in the direction of ...
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Why did Galileo use a ramp instead of a rope/pulley in his famous experiment?

If I understand correctly, one can derive an equivalent relation between distance the body falls and time, by using a rope/pulley system too. Conceptually it may be easier and perhaps more natural. ...
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471 views

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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1answer
115 views

Why is this system isolated (revised)?

(Image updated for clearance) Hello, Assuming that there is no friction anywhere and both box 1 and ramp 2 start at rest, I was wondering why this is an isolated system in terms of momentum ...
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2answers
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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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2answers
57 views

Are more wheels helpful?

Suppose A motorcycle is coming down a slope. Only gravity is acting. If we put 2 wheels more in that motorcycle, will the speed increase or decrease compared to normal 2 wheels? If more wheels are ...
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94 views

Will the hinge on a piece of wood affect the calculation for kinetic energy?

I was working on a problem of finding the kinetic that a point of a rectangular piece of wood will have after it swings and hits something. I have the following diagram: The rectangle has length $L$,...
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637 views

How to calculate resisting torque due to moment of inertia

I'm trying to determine whether a motor is suitable for an experiment. I know the motor's torque and the moment of inertia of the disk it will be turning. I was able to find the angular acceleration. ...
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3answers
513 views

Static friction free body diagram on a flat plane

Do you include static friction on a free body diagram for a static box on a flat surface? Or do you just include Force of gravity and Normal force? We know when the box is moving there is Frictional ...
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1answer
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When an object is moving, does air resistance build up after it begins to move or during?

For example,if a car is accelerating to 70km/h, when the car is at 35km/h, will air resistance also be at 35km/h or will it slowly build up after it begins accelerating?
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1answer
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Do nucleons experience friction?

I know that friction occurs because of imperfect surfaces rub against each other, and to my knowledge this occurs on the molecular level. However, since nucleons have spin, I was wondering if, since ...
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1answer
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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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2answers
181 views

Confusion about work done by a force in different reference frames

Suppose I have a little mass m resting on a big slab mass M resting on a table. There is a frictional force between the little mass and the slab, but not between the slab and the table. Suppose I now ...
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1answer
163 views

Conservation of linear momentum after explosion with friction

Let's say you have a bomb at rest submerged in a liquid. It then explodes into two equal fragments A and B which leave in opposite directions. If we ignore the fluid and any sound or light we can ...
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1answer
117 views

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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2answers
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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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1answer
584 views

Contact force between two boxes when static frictional force>external force

A question that my friend asked me but I can't figure out why the answer is C. Won't the block not move and net resultant force = -4.525? I haven't learnt about static and kinetic friction and am ...
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1answer
88 views

Conservation of Energy with Rotation Caused by Friction

A book that I am using to study poses the following problem: Suppose you wish to use a spring with a force constant $k$ to launch a spherical ball or radius $r$ and mass $m$ up a ramp of inclination ...
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1answer
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slip definition that works in game

Wikipedia article gives us the following 2 equations: $\%_{slip} = \frac{\omega r - v}{|v|} * 100$ (The use of $v$ modulus makes it work in all directions. It is multiplied by 100 to get the ...
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2answers
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If a block moves on a straight line (no friction) for time $T$ and then along an incline plane, what will the displacement vs. time graph look like?

In my opinion, the graph for the first part of the motion will be a straight line passing thorugh the origin (at the beiginning of motion) and then it will be a falling parabolic curve ( $x$ is ...
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1answer
99 views

Increasing frictional force without increasing normal force

Is it possible to achieve 10N of frictional force while only having 1N of normal force, using a coefficient of friction no greater than 1? My grade 11 physics teacher is asking us to do this. He ...
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158 views

Why does limiting friction have to act when a block tied to a wall is pulled?

A block lying on a rough surface, is connected to a wall by a mass less, inextensible string and an unknown amount of force is applied to the block opposite to the side of the wall. Now, if it is ...
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1answer
119 views

Unclear things about conservation of energy

I have started reading Feynman Lectures in Physics, First Volume, with absolutely no background in physics [*]. In the fourth chapter, conservation of energy, I am having difficulty understanding ...
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119 views

pulley friction assumptions

I have a dispute with this lecturer I have been given over the equation $T_2/T_1=e^{μθ}$. My opinion is that since it is derived from $T_2=T_1+\text{Friction}$, so the first equation is valid ONLY in ...
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3answers
812 views

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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482 views

Rolling Resistance Coefficient

I found that rolling resistance can be expressed with this equation: $$F_\mathrm{rr} = \frac{C_\mathrm{rr} W}{r}$$ Where $C_\mathrm{rr} =$ coefficient of rolling resistance $W =$ normalforce $r =$...
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Car wheel's “slip ratio” equation for game

Some of you may know about slip ratio. It is specific ratio that kind of depends on wheel rotation speed, radius etc. and affects friction. Car has the most friction at around 0.05-0.1 slip ratio (...
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2answers
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How to determine the friction constants

We know that the friction is formulated in this form $$F=av+bv^2+Nμ$$ I'm working with an object and surface and I want to find $ a, b, μ $ for them. Can you please give me an experimental method ?
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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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1answer
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Why is the friction vector resolved even though the inclined plane is the reference plane?

I do not understand why the frictional force is resolved even though it is already on the reference x-axis. Asked this question to college teacher and got reply,"I will do it later" and later never ...
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4answers
131 views

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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Rolling drag and action-reaction forces

I do not understand the two factors acting on the car during driving, they are Rolling drag which it is rolling resistance and action-reaction forces. If the Rolling friction reduces the the car ...
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109 views

Paradoxical Friction When Frying Eggs

I cook scrambled eggs for breakfast in an 8-inch diameter non-stick frying pan with sloping sides (approx 45 degrees). I cook the eggs in a lot of butter and bacon grease that is melted firest, so ...
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1answer
179 views

Plastic and Iron - static and magnetic

I'm wondering if when you have a ball that is made out of plastic but has an inner core of metal. Would that ball if given friction produce static? Or would the static from the outerside of the ...
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49 views

Dependence of kinetic friction on relative velocity

While I was reading my book I came across a line that tells that there is slight dependence of kinetic friction on velocity of relative motion of the bodies. Can anyone tell me how is this so?
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Frictional loss of matter

How do we account for the loss of matter from an object due to friction ? Is it simply a phenomenon or result of any other process ? Eg :The loss of matter from the rubber tyre
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1answer
381 views

Can an object be acted upon by both static and kinetic friction at the same time?

Why is it that, as soon as the 'required' static friction for no relative motion between two objects exceeds the maximum static friction, kinetic friction 'takes over'? Shouldn't static friction ...
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5answers
3k views

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

I have the following question: I noticed that if I solve for the acceleration assuming that the acceleration is occuring to the left, I get the equation: $\displaystyle a = \frac{m_3g-\mu_km_1gcos\...
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1answer
323 views

Will charge transfer without friction

I know rubbing two objects of different materials together will result in a negative charge on whichever material has a higher electron affinity. However, I was wondering if a negatively charged ...
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1answer
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What does the term “no slipping” mean in mechanics?

Say, I have two blocks. One block is on top of the other. Suppose friction is present everywhere. What is the condition for no slipping?
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Mathematical Mechanics - Friction Question (weight is laid upon an inclined plane)

A weight W is laid upon a rough plane [µ=1/(sqrrt3)] inclined at 45 degrees to the horizon. It is connected by a string passing through a smooth ring A, at the top of the plane, with a weight P ...
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3answers
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Kinetic Versus Static Friction Problem

Block one is on top of block two, with blow two on a frictionless table. The system of blocks is accelerating to the right due to a force applied strictly to block one. What direction is the ...
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3answers
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What is the minimal friction force required in order for a ball on an incline to roll without slipping?

I read an article now and it confused me completely. Since I thought I have read somewhere else a completely different solution. You put a ball on an incline at rest. What is the minimal friction ...
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1answer
342 views

Object falls off an inclined plane, what's the acceleration of the plane?

The problem statement is as following: "We have an object with mass m falling down, with friction, on the bigger object with mass M and tilted with the angle alpha. If the bigger object is moving ...
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1answer
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Question on Rotational mechanics

A plank with a uniform sphere placed on it, rests on a smooth horizontal plane. Plank is pulled to right by a constant force F. The sphere does not slip over the plank. I always get stuck in such ...
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1answer
41 views

Friction as a Centripetal Force on a disk

Consider the following: A rock is on a horizontal disk that rotates at a constant speed about the disk's vertical axis. Apparently the centripetal force in this case is friction. But from my ...