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

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Why friction force peak just before the object moving?

This diagram shows the amplitude of friction force of a typical contact-surface object. The friction force increases as we apply an internal force until it reach a maximum value just right before ...
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93 views

Does reducing the surface area between 2 objects reduce friction?

I am 3d printing a system where a gear like object is compressed against similar sized plates on both sides. However, for the first prototype there is too much grinding, making rotation difficult. I ...
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45 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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4answers
257 views

Why Do Objects move?

Let's imagine a block resting on horizontal table. When We apply a force which is greater than frictional force it moves. But why does this happen? Why can't friction withstand any force? As we know ...
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2answers
59 views

With friction, does the path followed from A to B affect energy transfer?

Consider I have a roller coaster that can travel across one of three paths, all of which are half circles of the same size. The half circle is an arch that starts vertically up, and ends vertically ...
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1answer
148 views

How can angular velocity be constant even when there is a torque by friction?

A cylinder at rest lying on a rough ground is given an impulse which imparts a translational velocity (no angular velocity) to it. The question goes ahead with finding time after which rolling starts ...
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1answer
1k views

Why does friction produce heat?

What causes two objects sliding against each other to produce heat? Why don't they generate visible light or something else?
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59 views

Friction related question [closed]

A uniform chain of mass $M$ and length $L$ is hanging from the table. The chain is in limiting equilibrium when length $l$ of chain overhangs. It is slightly disturbed from this position. Find the ...
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1answer
64 views

How to calculate torque needed to rotate a ring held captive between two parts with a known compression force?

I'm wondering how to find the torque needed to rotate a ring that is held captive between two plates with a known friction coefficient, radius, and compression force. I'm assuming that the mass of the ...
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6answers
6k views

Can a Skydiver Land On a Large Slide and Survive?

Please forgive my lack of artistic ability, but here's my question: Consider that a skydiver, without using his parachute, were to fall exactly parallel to a giant curved slide that starts at ...
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2answers
96 views

What should the brake force in this problem be? [closed]

Alright so I think I know how to do this but I require help in calculating what acceleration would be in terms of some sort of friction coefficient. So model a particle going down a hill. The slope ...
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2answers
52 views

Some confusion pertaining to direction of static friction on stationary object

Consider a stationary object of mass $m$ on a horizontal table. Since the object does not move relative to table, $f_s=0$. So it seems that we first consider $mg$ and normal reaction force,$N$ ...
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3answers
273 views

Determine direction of friction on a block held stationary against a vertical wall [closed]

A block of mass $m$ is pushed up against a wall and held stationary by a force $ F$ that makes an acute angle $\theta $ with the horizontal. May I know how to determine the direction of the static ...
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0answers
27 views

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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1answer
123 views

Explanation about friction force directions of two moving bodies in contact

can someone explain me why in this scenario (picture below) we have a friction force Ftr12 in the same direction as movement (left part of the picture, case 1 ) and how these directions of friction ...
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1answer
126 views

Consistent method for finding direction of static friction

I am having trouble coming up with a consistent method of determining the direction of static friction. So far the best I have come up with is: it should oppose the relative acceleration the contact ...
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1answer
76 views

Why don't things balance after they stop spinning?

When I spin a penny, I spin it on its "edge" (circumference). So why is it that when the penny inevitably stops spinning, it never comes to rest on its edge, instead falling onto one of its faces? It ...
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2answers
153 views

Kinetic friction with no force on an object

We've learnt that friction is the opposition of motion and that friction appears the instant a force is applied on an object i.e when an object is at rest (with no force acting on it) then there is no ...
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2answers
937 views

Why are tensions in the pulley different when the pulley has a mass or moment of inertia?

When two blocks are connected by a string passing over a pulley whose moment of inertia is given (means pulley is not massless) then why does the string not have same tensions?
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2answers
69 views

Will the gravitational pull of air affect the falling rate of an object?

After looking at this question: Don't heavier objects actually fall faster because they exert their own gravity? A thought occurred to me that due to the increased gravitational pull of the ...
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4answers
124 views

Why spinning a pen makes it easier to remove it from the stand?

I have a ballpoint pen stand on my desk. The pens are held inside their caps with the point down, like this one (but not as fancy): If I try to simply pull up one pen, the friction between cap and ...
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1answer
69 views

How can we account for a friction force changing sign in a conservation of energy equation?

I want to solve a simple mechanical problem whereby three forces act upon an object. $F_1 = (10 - x)$ N $F_2 = -3 N$ (friction force) $F_3 = -10x$ N So at $x$ = 0 we see that $F_1$ + $F_2$ + $F_3$ ...
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6answers
3k views

Conical train wheels

I've been reading about how the conical shape of train wheels helps trains round turns without a differential. For those who are unfamiliar with the idea, the conical shape allows the wheels to shift ...
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2answers
213 views

Showing that a mass moves a half cycle

Consider a mass $m$ at position $x(t)$ on a rough horizontal table attached to the origin by a spring with constant $k$ (restoring force $-kx$) and with a dry friction force $f$ $$\begin{cases} ...
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3answers
125 views

Velocity and acceleration with variable friction

If you have a body on a table,with a velocity $u_0$, going from a non friction area to a friction area, how do I find the function for velocity and acceleration due to the variable friction force(T). ...
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1answer
142 views

What is force of static and kinetic friction? [closed]

While I am asking more than one question in this thread they are all small concept tests that you can answer with a yes or no, and is all related to me understanding kinetic and static friction. ...
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4answers
308 views

A block sliding down a ramp lab (with friction), I keep getting a higher final energy than initial

A block of $\rm55g$ is sliding down a ramp of $35^o$ of inclination. The hypotenuse of the ramp is $\rm63cm$ and the height is $\rm36cm$. $v_i=0$ as the block starts at rest. I did 3 trials of ...
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Why is friction force negative in ice skater problem?

A 68.5 kg skater moving initially at 2.40m/s on rough horizontal ice comes to rest uniformly in 3.52s due to friction from the ice. What force does friction exert on the skater? I am not really ...
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1answer
358 views

How is inertia related to friction?

Inertia is the tendency for moving object to continue to move at constant velocity. My book says "in order to initiate motion in an object, inertia must be overcome to start the movement." But that ...
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1answer
85 views

Work done by friction on a ball flying through air [closed]

A baseball of mass 145 g leaves a pitcher’s hand at 150km/hr, but due to constant air resistance, it arrives at home plate 20.0m away traveling at 145km/hr Assume that the magnitude of the ball’s ...
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1answer
88 views

Does a propeller being pushed through the air have more friction if free to spin?

I just passed a boat being pulled on a trailer and noticed the propeller spinning in the wind. I began considering the possibility that a propeller free to spin might cause less friction against the ...
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3answers
148 views

How to apply Newton's first law to moving object?

I'm new to many forces, such as gravity and friction, and I don't really know how they work. I'm trying to simulate a ball bouncing with a program, and it travels at a constant speed horizontally. I ...
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2answers
86 views

A confusion regarding friction

Suppose there is a block which is being pulled by two forces A,B in opposite direction(as shown in figure). If we have no information regarding the forces $A$ and $B$, can we tell whether there is any ...
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14answers
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Is it possible to walk in a friction-less world?

Is it possible to walk in a frictionless world. I think you won't be able to walk because walking depends on friction acting on your feet. I think about it like an ice rink because when you try to ...
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1answer
72 views

How does a skater moves by pushing sideways?

Take a look at this video http://www.youtube.com/watch?v=EmMf91AVUXc or take a look at the following screenshot. As you can see, the skater pushes almost perpendicular to the direction of movement ...
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2answers
859 views

Does body weight affect the speed when going downhill on a mountain bike?

We know heavier objects fall faster when dropped at certain height. I was wondering if I am going downhill on my mountain bike without any peddling, will I travel faster or slower because I am fat?
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194 views

Friction as a Non-conservative force

Intuitively, one can find friction to be a non-conservative force. How can one prove that it is non-conservative?
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3answers
104 views

Frictional forces apposing motion

Please could someone help with some physics about resistive forces that would slow a ball down which is rolling across a floor. I have found conflicting bits of information about the effect friction ...
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2answers
218 views

Does rolling friction depend on area of contact?

We know that forces of static or kinetic friction do not depend upon the area of contact of the two surfaces, is it applicable to rolling friction as well?
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4answers
1k views

Does stopping the same bike and rider at the same velocity with the front brake require less energy than the back brake?

It's the same body made by the rider and the bike moving at the same speed. So, even though braking on the front/back alters the normal forces on the opposite wheels thus creating more friction with ...
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1answer
40 views

Are coefficients of friction invariant by switching the materials?

I don't have the ability to make the experiment to answer these questions : Let $A$ and $B$ be two materials. Is the static coefficient of friction of $A$ on $B$ equal to the static coefficient of ...
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1answer
84 views

Work done by friction on a body?

I know that when a body slides over a surface, the work done by friction is not stored as potential energy in the body. It is dissipated in the form of heat. But why is it not stored as potential ...
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2answers
1k views

Why is sliding friction more than rolling friction? [duplicate]

Frictional force doesn't depend on area of contact. So why is co efficient of rolling friction less than coefficient of sliding friction?
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25 views

Flow Rate Calculation from a drain tank through a pipe [duplicate]

I want to know how to calculate the flowrate (Q) of a drain tank flowing through a pipe (see the figure below) All I know is that Q=Velocity(V) x Area (A) V= sqrt(2*g*H)=sqrt(2*9.81*10)=14m/s. I ...
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2answers
189 views

Conceptual rolling

If you could roll a ball down a slope with friction, we would all know which direction the ball is rolling. However, say we have a frictionless slope and we roll the ball in the opposite direction and ...
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1answer
90 views

Damping a spring force

I'm modelling particles in a system using a spring and damper force. $$F= kx -cv$$ $x=x_i -x_f$, where $x_i$=centre of spring and $x_f$= displaced position. Above $x$ is the displacement and $v$ is ...
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2answers
2k views

What would happen if there was no friction on earth? [closed]

I'm not talking about zero-g or a vacuum. If oxygen, gravity, air pressure, etc still existed but if there was suddenly no friction, anywhere.
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5answers
207 views

Why does solving $\mu mg = m \frac{v^2}{r}$ give the *max* possible velocity?

So here is the standard problem setup of a car turning on an unbanked road: A 1000 kg car is going around a curve with radius 30 meters. If the coefficient of friction between the car's tires ...
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1answer
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About friction contributing to speed

Friction in our daily experience is understood as a resisting parameter to the effort putted for moving an object on a surface. I understand friction as a negative force by describing what happens to ...
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3answers
3k views

Can negative friction exist? If so, what happens?

I have to talk about negative friction for my oral exam and I would like you to comment my presentation. I know that friction is the resistance to motion that occurs between objects. So friction is ...