Questions tagged [friction]

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

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1answer
782 views

Maximum friction force for a wheel to be able to roll

The wheel with mass $M$ and radius $R$ below is free in space (it is not on the ground). A torque $\tau$ is applied to it through an engine. A horizontal force $F = \frac{\tau}{R}$ is also applied to ...
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1answer
262 views

Is there any situation when oil increases friction?

I have read everywhere and tried myself to experience oil smoothening surface interfaces, thereby reducing friction. I was curious if there are instances where oil increases the friction between those ...
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1answer
150 views

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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55 views

The origin of normal reaction

I want to know what actually is the origin of normal reaction between 2 objects. i have read about normal reaction from several books which generally mention it as a component of contact force which ...
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0answers
24 views

Calculate the time taken for a body to hit earth's surface [on hold]

Find the time taken for an iron cube of dimensions 0.1m × 0.1m × 0.1m, whose density is 7.85 g/cm³ to reach the earth's surface released from a height of 10m from earth's surface, provided gravity = 9....
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1answer
23 views

A Chain in Equilibrium

My By book says that, for equilibrium Limiting Friction$(f_L)$$=$Weight of hanging chain. But Why??
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1answer
81 views

Derivation of equation of motion for mechanical seismograph

Consider a simple seismograph consisting of a mass $M$ hung from a spring on a rigid framework attached to the earth, as shown in the picture. The motion of the mass is apparently described by the ...
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3answers
988 views

Thermodynamics and Newton's second law

Is it correct to say, that the Newton's laws (or a Newtonian system) is reversible if the friction isn't considered (the fact that the time is of second order $\frac{d^2x}{dt^2}$) and an isolated ...
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1answer
2k views

Why friction force is force of constraint?

My understanding about constraint force is that it is a force which limits the geometry of particle's motion. For example, situations such as the particle trapped in a track or limited in domain can ...
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3answers
179 views

Total force on upper block in two block system

If a block $m$ is placed on another block $M$ and a force $F$ is applied on bolck $M$. Then how many forces are acting on block $m$.(Friction is non zero) The image is taken from this site. Is ...
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1answer
40 views

Why do we consider the viscous force to be tangential?

Is it that since it is a friction force, it needs to be tangential as other friction forces like kinetic friction and static friction forces are?
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2answers
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Can someone explain these circled points…?

Why is direction of friction in the direction of motion and here it is the platform that moves....the movement is not caused by friction so how is friction doing work? In the second one there is no ...
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2answers
36 views

The reason behind circular motion of vehicles

In all the textbooks and internet resources that I've ever read , most of them explains role if friction in circular motion of an object (let's says a cycle), from the frame of the cyclist i.e. with ...
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35 views

Friction and Circular Motion

In circular motion, it is said that the friction acts towards the centre of the circular path. But friction opposes tendency of relative motion and since the velocity of the body(in circular motion) ...
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860 views

Physical Interpretation of an Overdamped Pendulum

Consider a damped pendulum whose equation of motion is given in general by $$m\ddot{x}=-\mu\dot{x}-kx$$ where $\mu,k>0$ Rewrite this equation as $$\ddot{x}+2\gamma\dot{x}+\omega^2x=0,$$ where $...
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A tough integration based problem [closed]

A massless rope is tossed over a wooden dowel of radius $r$ in order to lift a heavy object of weight $W$ off the floor. The coefficient of sliding friction between the rope and the dowel is $\mu$. ...
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41 views

How does friction cause a spinning top to fall?

I am wondering how friction can create a torque to change the angular momentum and cause a spinning top to tilt, like in the diagram of a close up of the rounded tip of a top while the angular ...
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2answers
93 views

Why does a car which decelerates slowly on a icy road not slip but a car which decelerates quickly does?

Why is it that braking slowly on an icy road is safer than braking quickly. Intuitively it makes sense but what is the logic?
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2answers
104 views

Why can I not draw with a pencil on my hand, while a pen works perfectly?

As far as my understanding goes, a pencil is able to write on paper, because of friction, bits of graphite re scrapped of from the lead. But then why is it that it doesn't work on my hand?? A hand is ...
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1answer
77 views

Why can't $U=b\mathbf{v} \cdot \mathbf{r}$ be considered a potential for the drag force ${\bf F}=-b {\bf v}$?

Consider the function $U(\mathbf{r},\dot{\mathbf{r}})=b\mathbf{r} \cdot \mathbf{v}=bx\dot{x}+by\dot{y}+bz\dot{z}$, where $b$ is the drag coefficient. Why can't this be considered as a potential energy ...
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461 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
28 views

$\mu_k$ of surface from experimental vs theoretical acceleration [closed]

I have an air track at a slight angle with a glider. Final velocity is determined, and from that a is calculated, and from a, I have approximated g. I am trying to find $\mu_{k}$ between the track and ...
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2answers
68 views

Objects traveling through water

If an object travels through water fast enough, can it create enough friction to burn? I'm sure a human could get to the point where their skin would become red the same as a belly flop. But what ...
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0answers
24 views

Free body diagram [duplicate]

I was reading about the ABS brakes and the articles say the wheels don't slide on the floor and the tire friction is static. but what would the force diagram of a tire look like under ABS? Wouldn't ...
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1answer
926 views

Damping coefficient and damping ratio

I am not sure if I understand the term damping coefficient correctly (I am a high-school student). Here's the link for the info that I learned: http://hyperphysics.phy-astr.gsu.edu/hbase/oscda.html ...
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2answers
48 views

How is the angle same in friction force? [closed]

How is the angle $\theta$ of the plane and between the $mg$ (attraction due to gravity) and component of $mg$ is same? In the figure $\theta$ between the $mg$ and its component $$mg\cos\theta$$ is ...
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1answer
8k views

Work done by friction

Suppose we have a block of mass $M$ and we are moving it up a curve, very slowly ($a=0$). The surface is not smooth, and coefficient of friction is $\mu=\mu_s=\mu_k$. To move the block we apply a ...
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1answer
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Work done by friction on an inclined plane

A rough inclined plane is placed on a cart moving with a constant velocity u on horizontal ground. A block of mass M rests on the incline. Is any work done by force of friction between the block and ...
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2answers
102 views

Isn't friction on an incline coefficient of friction times the Reactional force?

Question - "As shown in figure a body of mass 1 kg is shifted from A to D on inclined planes by applying a force slowly such that the block is always in contact with the plane surfaces. ...
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6answers
637 views

Why does the friction act on the inward direction when a car makes a turn on a level road?

I tried looking this question up online but am left a little confused with all the answers, and the diagrams. When a tire of a car negotiates a turn in the road, there exists friction which is ...
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2answers
2k views

Does a tire need to slip to generate force?

Recently, I have been doing some research on racing and tire modelling. While I was doing this, I encountered many curves like those shown below. (source: insideracingtechnology.com) While I ...
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1answer
118 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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Maximum acceleration on a turn

The question $\\$ Suppose a car enters a turn with an initial speed $\vec{v_1}$, and comes out with a final speed $\vec{v_2}$ perpendicular to the direction of $\vec{v_1}$. The driver does everything ...
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1answer
28 views

What's the “cause” of damping coeff. in springs?

What's the "cause" of damping coeff. in springs? Air resistance, friction?
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6answers
7k views

What force enables us to walk? Friction or normal reaction?

I know that this question has been asked here before, but I am a little bit confused with all the answers. So when we move, we apply force on the ground in the backward direction. So, is the ground ...
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3answers
164 views

Basic question on friction

Consider the whole system initially at rest.Suppose there is friction between the blocks, but not between the lower block and the floor. Suppose I apply a Force F to the left over M, with F greater ...
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2answers
48 views

What is the exact role of friction in rolling without slipping?

When an object rolls along a plane, we say that for the object to roll without slipping, the velocity of the center of mass must be equal to angular velocity times radius, so that at the point of ...
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3answers
92 views

What helps us carry things around? [closed]

Say I move from point A to point B. I carry an apple in my hand. What causes the apple to move from point A to B? In other words, what force is responsible for keeping the apple stuck to my hand and ...
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1answer
135 views

Physical interpretation of time constancy in damped harmonic oscillator

I know that one can mathematically derive and prove that in a damped oscillator (without external driving) the time period of oscillations is a constant. But how can one physically interpret as to why ...
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2answers
125 views

When you have engine at idle and turn your car, where does the kinetic energy go?

When you turn the front wheels to the right for example, your car will tend to continue in its original forward direction. However, there is friction between the wheel and the ground that prevents it ...
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1answer
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Drifting vs. rolling when starting race

Imagine you are about to start a car race. You are on the grid, waiting for the green light. What should you do in order to optimize your start? Some people would say that a drift start would be the ...
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3answers
12k views

Effect of steering a car at high speed

I take it the angle of the steering wheel in a car is roughly proportional to the curvature, and therefore inversely proportional to the turning radius. When I am driving slowly and want to turn the ...
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2answers
179 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
138 views

Effect of forces inside a sphere

What would be the effect of applying two parallel forces of the same value at opposite points of the equator inside a sphere? Common sense tells me that it wouldn't move, but it seems that it could ...
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2answers
127 views

Frictions in a slowing car

When you apply the brakes to a car and it slows down, there are two kinds of friction and I am getting confused. On the one hand, there is friction between tyres and road. This friction a) Is the ...
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1answer
328 views

Is kinetic friction still constant at the transition from static to kinetic friction?

I'm looking at this graph from here: The answer providing the above graph explains how kinetic friction is constant. However, the graph tells me that after static friction is overcome, there is a ...
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0answers
270 views

Extension of the Capstan Equation

The Capstan Equation relates the holding force and the load force for a string wrapped around a cylinder. However, most people who work with heavy machinery know that if you wrap a rope around a post ...
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3answers
160 views

Is the “efficiency” of car brake affected by how much force is applied by the brake?

Someone argues with me that stepping on a car's brakes for long periods of time will wear out the brakes faster than applying the brakes for short periods of time. We were talking about stepping on ...
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3answers
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Can we know when rolling occurs without slipping?

In school we solve a lot of physics problems involving rolling cylinders/hoops/wheels. Often it is specified in the question statement that "rolling can be assumed to occur without slipping". Then we ...
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3answers
56 views

Rolling without slipping forward force

I'm studying rolling without slipping, I want to find the net force making a wheel go forward when applying a torque about the axle of the wheel. In this page https://www.school-for-champions.com/...