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

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2answers
48 views

Velocity of a body in a pulley problem involving a spring fixed to the ground

So the picture shows the whole situation. My question is, how do you find the velocity of the object after it had descended 10 cm (0.1 m) ? Pulley's radius 0.2 m, moment of inertia 0.2 kg/m I ...
7
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2answers
239 views

Damped oscillator: time-reversal, time-translation and dissipation

The equation of motion of a damped oscillator $$\frac{d^2x}{dt^2}+\gamma\frac{dx}{dt}+\omega_0^2x=0$$ which is invariant under time-translation $t\rightarrow t+a$, but not under time reversal ...
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0answers
17 views

Find the Work Done in this system [on hold]

In Inclined plane if friction force = the weight of the object. What is the total work done by this system?
2
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3answers
306 views

What is the relationship between rolling resistance and velocity?

I'm a games programmer, trying to write a simple car physics simulation. I'm aware that a car travelling in a straight line will exert a traction force that drives it forwards (by turning the wheels ...
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1answer
237 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 ...
-1
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0answers
19 views

At which points Normal reaction acts on a moving object is more , if possible give an image for this , A,B,C,E . Thanks For Answering [on hold]

At which points Normal reaction acting on this moving object is more. We know that friction of a rolling body depends on the Normal Reaction Force. Situation 2 is the latter of situation 1 .I just ...
3
votes
3answers
282 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 ...
0
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2answers
21 views

The direction of frictional force in circular turning

Why does the frictional force in case of circular motion point towards the center even though the motion is tangential to the radius?
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1answer
40 views

What kind of damping is this $F = -ax|x'|$?

From Applied Mathematics by Logan: A mass hanging on a spring is <...> governed by $$mx'' = -ax|x'| - kx$$ where $-ax|x'|$ is a nonlinear damping force. I looked up "nonlinear damping" ...
0
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2answers
247 views

We cannot solve this inclined plane problem, right? [closed]

We drag a sledge along a snow-covered hillside with constant speed. Distance is 150m. The time it takes to reach the top is 300 secs. The sledge is 12kg. And the coefficient of friction $\mu$ = 0.04. ...
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vote
1answer
194 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 ...
3
votes
1answer
601 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 ...
13
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4answers
17k views

After what speed air friction starts to heat up an object?

I understand that air friction cools off an object at low speeds. For example, if you blow on a spoon of hot soup, it cools off. Or if you swing a hot frying pan in the air, it cools off faster. But ...
2
votes
1answer
57 views

Problem on rotation

So this is the problem:A wheel of radius of gyration k is placed on a belt moving with a speed v, which is maintained constant by means of an external agency. Assume that the axis of the wheel is ...
10
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2answers
2k views

Hydrostatic friction: why do water droplets stay at rest on an inclined glass surface?

This is a non-expert question on a (seemingly simple) text-book topic. The question is about "hydrostatic friction", defined as follows. Consider a drop of water resting on a flat surface. If the ...
1
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1answer
37 views

Slow-Roll: What is the energy of a scalar field transformed to due to Hubble friction?

So, I've lately been reading about the Slow-Roll approximation of scalar fields. However - since I don't really know that much about cosmology - I have some trouble regarding the understanding of the ...
2
votes
2answers
52 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 ...
1
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1answer
107 views

Air friction at supersonic velocities

I know that if an object moves in the air, it can experience two types of drag, laminar and turbulent. For instance, I have a meteor of ideal spherical shape falling from edge of space, say, 100 km up ...
4
votes
1answer
66 views

What is the specific source(s) of sliding kinetic friction

In simplistic (K-8) physics classes, it seems to be generally instructed that the friction between two moving surfaces is due to the unevenness of each surface and the microscopic roughness. However, ...
1
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1answer
137 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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1answer
31 views

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 ...
3
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3answers
81 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 ...
0
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1answer
156 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 ...
3
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3answers
74 views

Why is the rod moving to and from?

These are tow pulleys, and a plastic plank is placed above them which can slide freely. The plank has uniform density and it touches both the pulleys. Both pulleys are placed on the same plane, and ...
0
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1answer
26 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
57 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 ...
0
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1answer
117 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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1answer
178 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 ...
0
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2answers
39 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 ...
0
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3answers
25 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 ...
0
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2answers
43 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 ...
0
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1answer
40 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 ...
0
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3answers
210 views

Confused about the direction of friction force

I'm really confused about the direction of friction force. I think about collision of two balls and think that "friction force is opposite to the relative speed of the contact point of the two ...
0
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2answers
28 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 ...
0
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2answers
63 views

Damped Pendulum (generalised)

I know the differential equation for the swinging of a simple pendulum: $\displaystyle\frac{\partial^2\theta}{\partial t^2} + \left(\frac{g}{L}\right)\sin\theta = 0$ where: $L$ is the length of ...
0
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3answers
2k 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 ...
3
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2answers
66 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 ...
0
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2answers
227 views

Can friction change the resonance frequency of a system?

I am simulating the transient response of a mass-spring-damping system with friction. The excitation is given in the form of a base acceleration. What I am not sure about is: can the friction change ...
4
votes
3answers
335 views

How does mass affect the distance a ski jumper travels

I did an experiment to explore this. My results found that their is an optimum mass of a ski jumper. I am unsure about the maths behind this. Can anyone help.
2
votes
1answer
273 views

Maximum angle for highway lane change

I am preparing to fight a traffic ticket from a speed camera. There is a lot more to that story, but the info I need right now involves the angle at which a car can change lanes, in terms of vehicle ...
0
votes
1answer
20 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) ...
0
votes
1answer
135 views

Rolling Friction Problem

The handbrake of a vehicle of mass $1.5\ \mathrm{tonnes}$ completely fails while it is parked on a $30^\circ$ slope. It rolls $20\ \mathrm{m}$ down the slope before colliding with, and locking on to, ...
0
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1answer
559 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 ...
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1answer
33 views
23
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3answers
2k views

Why doesn't a fly fall off the wall?

Pretty simple question, but not an obvious answer at least not to me. I mean you can't just place a dead fly on the wall and expect it to stay there, he will fall off due to gravity. At first I ...
4
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1answer
2k 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?
0
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2answers
3k views

The direction of frictional force in smooth rolling motion

I want to ask about the direction of frictional force in smooth rolling motion which means the rolling object doesn't slide on the surface. Here is the first case, the wheel rolls to the right so the ...
0
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0answers
21 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
votes
3answers
108 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 ...
1
vote
3answers
312 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 = ...