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

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Non-uniform Normal force, friction

I got problems understanding the Non-uniform normal force. Why is it non-uniform? Because the object would have different densities in different parts, so weight would be greater in some parts? So ...
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1answer
28 views

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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1answer
63 views

Equation of Motion for spring-cylinder-mass system [closed]

Hello, I hope someone can help me with this question, to find the equation of motion of the disc for small angular rotations. The mechanism comprises of a uniform circular disc of mass $m$, spring ...
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2answers
42 views

Damped Simple Harmonic Motion Proof? [closed]

I was reading about damped simple harmonic motion but then I saw this equation: $$-bv - kx = ma$$ $b$ is the damping constant. Then it said by substituting $dx/dt$ for $v$ and $d^2x/dt^2$ for $a$ we ...
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3answers
26 views

Are polished materials (say concrete/stone), more impervious to surface explosions?

Maybe another way to word this / a specific example: Is an object's resistance to damage from an explosion at all effected by it's smoothness / lack of friction on the surface? Example: Say an ...
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1answer
42 views

Rotating mass and gravity effect [closed]

I'm a 57 yr old EE, but never had any mechanical physics classes. If we have a vertically oriented disc, affixed to an axle in bearings, 1m in diameter, with two 1kg weights attached at the outermost ...
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2answers
48 views

is the nature of friction forces chemical or mechanical or both or other?

I don't quite understand the nature of friction forces, in simple mechanics and also in fluid mechanics. Is the nature of these forces, intermolecular forces ie. chemical nature? Or is it ...
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2answers
33 views

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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73 views

Pulley rotation

In the given arrangement, the friction in between the string and the pulley is enough to avoid slipping and the string is light. On the basis of these assumptions, would the tension in the upper part ...
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1answer
24 views

How does gas friction emerge?

The fluid parcel model states that a gas can be modelled as the sum of infinitesimal small parcels. According to this model, the friction of a gas with a solid surface (e.g. the wall of a pipe) ...
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1answer
49 views

What is the amount of Power required to maintain a flywheel at an angular velocity $\omega$ rad\sec of mass $M$ kg and Radius $R$ m? [closed]

What is the amount of Power required to maintain a flywheel at an angular velocity W rad\sec of mass M kg and Radius R m ?
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22 views

How does the rolling resistance of sticky tires scale with speed?

If I have a wheel that has a soft tire that sticks to the ground, will the rolling resistance (not the traction of the wheel, I mean how much force it takes to keep it rolling at the same speed) scale ...
3
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3answers
128 views

Is static friction the only force causing a car to move (without sliding)?

A car is moving without sliding means that the friction between wheels and the ground is static friction. This is the force causing an object to move forward, therefore, its direction is the same as ...
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2answers
97 views

Why does a ball eventually stop?

I was wondering, if the force of friction with the ground does not make any work on the ball and just give it the necessary torque to rotate (hence the consideration of static friction coefficient in ...
3
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3answers
54 views

Why does a pot start rotating when coffee is stirred inside?

I usually make Turkish coffee as my morning coffee. I have a small somewhat rounded pot with handle on one side. I noticed that when I pour water in and start stirring, pot has a tendency to start ...
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141 views

Difference between stiffness and damping?

I understand stiffness as the extent to which an object (e.g. a mass spring) resists deformation from an applied force, or the rigidity of an object. And I understand damping as the energy ...
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1answer
60 views

Circular motion and inclined friction [closed]

I'm given the following picture: A car with the mass m passes the top of a hill with the height H. The coefficient of friction is $µ$. The speed of the car is $v_0$ in the moment of braking. ...
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2answers
30 views

Will kinetic friction change when normal force and coefficient of friction remains the same?

Based on common knowledge, a car can do uniform motion in any velocity when the applied force(by engine) do not exceed the maximum kinetic force of friction which can be calculated by: $$\ F_f = \mu_k ...
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1answer
22 views

The instability of dry friction

Based on Newton Dynamics, the kinetic force of friction of any moving object can be found by using formula, $$F_f = \mu_k F_N $$ This means that if $\mu_k$ and $\ F_N$ remains constant, the ...
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39 views

Can't identify static and kinetic friction regions

EDIT:I would like to say thank you to those who have commented so far trying to help me. It is really appreciated!! In a project, I am analysing the frictional behaviour of different specimen on a ...
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0answers
32 views

Pendulum with Viscous and Frictional Damping

I am trying to model a pendulum with both viscous and frictional (Coulomb) damping. The problem is that the viscous damping only occurs in one direction because I am modeling a dashpot that only has ...
3
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3answers
83 views

When only part of the surface an object is in contact with has friction, what is the normal force I should use?

I have the following exercise: A uniform rod of mass $M$ is given a horizontal velocity $v$ on a rough track as shown in the figure. The surface is rough on the right side of the origin $O$ and ...
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1answer
101 views

How to calculate torque required? [closed]

Here's my problem diagram: I am working on a hobby project in which a motor is required to rotate a pulley that is connected to a pendulum as shown in the image. The maximum torque, Horsepower and ...
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1answer
16 views

Do dimples reduce laminar drag across a surface?

My question is about laminar flow across a smooth surface. I have read about how the eddy currents, caused by dimples, at the surface help a blunt object travel through the air with less drag as in a ...
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1answer
22 views

Problem involving Energy Method and Non-conservative Forces [closed]

I've got a problem in my physics I class that's got me stuck at the moment. A box is placed onto an angled plane so that it compresses a spring. When released, how far up the plane does the box go? ...
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1answer
70 views

Friction of a scissor [closed]

How can the friction by a scissor blade be related to its angle? To be more specific this is the question that I came across. A scissor is used to cut a wire of circular cross section and ...
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1answer
29 views

When to consider friction as an impulsive force?

Suppose a ball obliquely strikes a rough horizontal surface then it experiences a frictional impulse and conservation of linear momentum cannot be done on the horizontal direction. Now consider ...
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2answers
60 views

How can you tell if the work done by a force is negative?

This is kind of confusing to me. I'm guessing that it's specific to the problem. Is the work done by friction always negative? Is the work done by gravity always negative? Spring as well? It seems ...
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1answer
53 views

Friction forces on stack of blocks

Consider a block sliding on a surface, with friction between the two. The friction force will be equal to $\mu N$, where $N$ is the normal reaction force, which is usually equal to $mg$, where, $m$ is ...
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1answer
65 views

Angular Acceleration of a Pendulum

I am trying to work out the mathematics behind the design of an old mechanical brake tester. The device sits in the passenger foot well of a vehicle and tests the brake efficiency. The device is ...
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1answer
22 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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1answer
37 views

Rheological Definition of Friction

I was listening to a record at our university about friction and its rheological definition. For the first moment I thought that its the normal definition Friction is the force resisting the ...
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0answers
53 views

Force conversion in a barrel cam-follower mechanism

A barrel cam-follower mechanism consists of a (cylindrical) barrel with a cam track, a cam-follower (roller) inside of the track, a fork connected to the cam-follower and a guide along which the fork ...
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21 views

pulley friction difference between static and sliding surfaces

the pulley friction question for static cases is T2/T1=e^μθ. When the surfaces between the belt and the wheel slide, how can we determine the friction? Is it the same friction? Is there a different ...
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2answers
42 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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7answers
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Why doesn't an object, despite having a non-zero potential energy stored in it, fall by itself from the elevation?

When an object is at a certain height, it has some energy stored in it as we have done some work on it to get it to that height. So when it already has energy, then why doesn't it fall off from the ...
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1answer
28 views

Understanding role of friction in block on block problems

Consider two blocks stacked on top of one another. There is friction between the blocks but there is no friction between the lower block and the table. So the only frictional force that tends to ...
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2answers
59 views

Dissipation and first law of thermodynamics

Consider the following situation: a certain gas is contained in a well-insulated cylinder with a well-insulated piston head. Now, in this case the piston is not frictionless. In order for the piston ...
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36 views

When will a moving vehicle stop faster: when the brakes are applied and the wheels are slipping, or just before? [closed]

When will a moving vehicle stop faster: when the brakes are applied and the wheels are slipping, or just before the wheels start slipping? Explain why.
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1answer
61 views

How I think about rolling [closed]

Below, I have written how I think about rolling. I wish to know if my idea as to how it works is correct. Consider a rigid ball on a plane which has considerable friction. If you push the ball ...
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1answer
52 views

Question about friction in rolling without slipping?

I was under the impression that for a ball/cylinder to roll without slip, there must be a static friction force that opposes the direction of motion. Why, in this case, does the friction act in the ...
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0answers
52 views

Find the maximum force P that can be applied for which the blocks do not slide and their respective acceleration

Two blocks are on an inclined ramp of 35 degrees. Block A is on top of block B. Block A weighs 36 lbs and block B weighs 18 lbs. The coefficient of static friction between the two blocks is 0.45 but ...
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1answer
43 views

How to find the direction of friction in rotation?

Suppose we have a spool which is plucked constantly from top with a force F. The spool is on a rough ground. We have to find the direction of friction, nd direction of motion of spool. ...
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2answers
75 views

What Feynman meant in description of reversible machine and levers

In chapter four of the part one of the lectures, he mentions: (..) A machine that we actually use can be, in a sense, almost reversible: that is, if it will lift the weight of three by lowering ...
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3answers
177 views

What happens to the coefficient of friction as the normal force increases?

Does the frictional force increase as the normal force increases, or does the coefficient of friction get smaller in value?
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1answer
50 views

Work done by friction on a conveyor belt [closed]

At a factory, a 300-kg crate is dropped vertically from a packing machine onto a conveyor belt (I apologize for not having a picture) moving at a speed of 1.2 m/s. The coefficient of kinetic friction ...
0
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3answers
69 views

Coefficient of friction

I know that coefficient of friction=f/N , and I also know that it depends on that surface area of contact and the material. But my doubt is ,from this formula if N is halved then coefficient of ...
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40 views

Energy dissipation in spinning wheel

I was given the following question in a test. A spinning wheel A is brought in contact with an identical wheel spinning at identical speed.The wheels slow down under the action of friction.Which ...
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1answer
124 views

Final Velocity of an object on Parabolic Curve

I decided to participate in a school challenge involving launching a marble off a curved ramp from a given height and determining the distance the marble will travel. I can no longer participate, ...