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

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2answers
28 views

Block over a Block Problem.

This a block placed on block problem. In this problem, A block with mass 40 kg in placed on a block of 60kg which lies on a frictionless surface. The coefficient of friction between 40kg mass and 60kg ...
0
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0answers
17 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 ...
-1
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1answer
26 views

Time taken for sliding mass to fall down

Figure shows a small block of mass m kept at the left end of a larger block of mass M and length l. The system can slide on a horizontal road. The system is started towards right with an intial ...
32
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3answers
6k views

Push a Boeing 737 on ice: Did this guy have a chance? [on hold]

In this video an airport worker (in blue) tries to prevent a Boeing 737 from sliding on ice in heavy winds: Did he even have a chance? On one side of the argument, the airplane is sliding due to ...
-1
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0answers
23 views

Frictional pulley [on hold]

Whenever we do any pulley problems, generally, it is mentioned, that the pulley is $massless$ and $frictionless$. But, what will happen if it is given that the pulley is frictional. I had gone a ...
0
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1answer
418 views

Walking and Friction

If walking is a result of the reaction to a kick backwards to the ground (reaction being friction), it appears that it should be true that the kick will have to be less than the kinetic friction ...
0
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2answers
86 views

If the force of friction is 20 N for a moving body does acceleration increase with the increase of the mass?

A body is moving and the only force acting on it is the force of friction. If we put another body on this moving body somehow the force of friction will increase; does its acceleration change?
3
votes
1answer
316 views

Rolling a ball into a cone; what should the forces overall be?

This is my solution to finding angular displacement/velocity/acceleration on cone so far. Consider a cone, with an apex of half-angle $\psi$ pointing down, and a height of $h$. If I roll a ball into ...
0
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1answer
30 views

When you smooth-en a surface at microscopic level, friction increases. Why?

When I was learning a chapter related to Static electricity, my teacher had mentioned that when you rub your comb with DRY hair specifically, static electricity is generated due to friction. Further ...
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2answers
43 views

Direction of frictional force

How will I find the direction of frictional force for any kind of motion of a moving object?
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2answers
48 views

How does friction act on a body, if only 2 regions on it are rough? [on hold]

While tackling an Olympiad question, it came to my mind that friction need not act in the same direction at all points on a body. I thought of using integration to evaluate the net frictional force, ...
1
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1answer
49 views

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 ...
0
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4answers
122 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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0answers
15 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 ...
1
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2answers
115 views

What is a self adjusting force?

What is a self adjusting force? I searched it everywhere on internet but not got my answer and I have no other source to get its answer except this site so please help me.
1
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2answers
47 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 ...
0
votes
1answer
63 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 ...
0
votes
2answers
97 views

Damping Constant for a Ball Rolling in a Bowl

How would you find the damping constant of a ball rolling without slipping in half of a sphere? I know how to find the period of the oscillation, but how would I find the damping constant ...
0
votes
1answer
346 views

Block Sliding Down a Plane (Perpendicular Velocity)

I'm having trouble understand the concepts for this problem. Here's the problem: A block is placed on a plane inclined at angle $\theta$. The coefficient of friction between the block and the ...
49
votes
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 ...
0
votes
1answer
38 views

Friction between two bodies placed one above another [on hold]

I'm recently facing a bit confusion regarding the friction between two bodies. Suppose there's two bodies, one placed on another. There is frictional force $ f $ between the base body and floor and ...
0
votes
3answers
271 views

Friction in Physics

I've heard a lot of things about Friction like friction between solids, liquids and gases. Even practical applications like motion of objects (Like car moving on road), etc. involve friction. But, do ...
8
votes
5answers
2k views

Pulling apart two interleaved phone books

The TV show Mythbusters had an episode in which they interleaved two phone books and dramatized how hard it was to pull them apart. (A long time ago, a phone book was a book that had an index of phone ...
2
votes
1answer
48 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?
1
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0answers
51 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 ...
0
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1answer
16 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 ...
0
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2answers
53 views

If two bodies move opposite to each other when brought in contact, what is the direction of force of friction?

We know that when a body is at rest and other is dragged over it then a force is produced which opposes the motion and consequently its direction is negative to the force applied on body to produce ...
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2answers
49 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 ...
4
votes
5answers
2k views

Would a three wheeled vehicle be faster than a four wheeled vehicle of the same weight?

If I have a four wheeled vehicle (small wooden block with metal nail axles and plastic wheels) and apply a force X to it, would it be made faster by keeping one wheel off the ground in order to reduce ...
0
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3answers
61 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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2answers
20 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,$N$ ...
0
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0answers
16 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 ...
0
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3answers
1k views

Different directions of frictional force when objects are rolling

My textbook has two instances of rolling bodies (smooth rolling). In the first, the body is rolling on the horizontal floor with some acceleration of its centre of mass. In this case, the book says ...
0
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1answer
122 views

Inclined plane, circular motion and the friction

Suppose we have a cylinder on an inclined plane of mass $m$ and radius $R$ moving without sliding (so that $\varepsilon = a/R$). Why is the friction $F$ causing the circular motion sometimes lower ...
3
votes
1answer
139 views

Is it possible to eliminate Van der Waals interactions?

I came to know that the friction force actually depends on the surface contact area due to weak interactions (adhesion due to Van der Waals forces) between the atoms of both materials increasing in ...
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1answer
39 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 ...
3
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1answer
197 views

Sliding ruler on table top

I've got a standard foot-long flat plastic ruler (about an inch wide) and a desk with a smooth formica-like surface. When idly passing time reading on the computer, I will pick up one side of the ...
3
votes
3answers
449 views

Would this box on the floor rotate based on friction?

There is a floor that friction is proportional to its velocity (like $F=-kv$) and there is a box with its width as $l$ and its height as $h$. (you may assume that $l$ is longer than $h$). It is on the ...
2
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2answers
203 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} ...
0
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1answer
72 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 ...
0
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2answers
72 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 ...
0
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0answers
23 views

What's the best way to avoid slipping on ice? [migrated]

Where I live, winter is still a good bit away, but last year I slipped on ice and ended up with a black eye and a broken wrist. This year I sincerely want to reduce the chances of that recurring. I ...
2
votes
1answer
59 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 ...
0
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2answers
48 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?
1
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4answers
91 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 ...
2
votes
2answers
51 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 ...
1
vote
1answer
52 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 $F_1$ + $F_2$ + $F_3$ ...
19
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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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3answers
54 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). ...
0
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1answer
46 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. ...