# Tagged Questions

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

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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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 ...
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### 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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### 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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### 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, ...
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### Why is Torque Generated from Friction?

Why does a rolling ball get torque from friction. I understand torque in relation to lever arms and the force being perpendicular to said arm. But what about wheels? There is no lever arm so how is ...
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### Where can I find a table of rolling friction coefficients of various materials?

I am looking for the coefficient of rolling friction of a 1.5 cm radius polymer ball rolling on steel. I have been searching all over the Internet for it but I can only find tables of static and ...
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### 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 have ...
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### What makes the magnitude of the force of friction velocity dependent in one scenario, but not the other?

When a solid objects makes contact with another solid object, I believe the magnitude of the force of friction between them does not depend on the relative speed of the two objects. When a solid and a ...
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### Apart from friction what can be considered a non-conservative force?

I know that friction is a non-conservative force. My question is if we have any non-conservative forces or other fields in electrodynamics? second part question for a force that conservative we have ...
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### About the formula of pendulum simple

for the modulation and the simulation of a pendulum simple , I'm Find this formula : a(t) = a0 * sin ( sqrt(g/l) * t * Pi/2 ) - [ k/(mll) * cos ( sqrt(g/l) * t * Pi/2 ) * t ) ] ...
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### Effect of friction on a moving body under a variable force

Given the system in the figure: The block slides on a horizontal surface and is acted upon by a force $P$ which varies in magnitude as shown. Knowing that the coefficients of friction between the ...
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### If a disc is rolling on a surface, how do you verify that no slip occurs? [closed]

If I have the values for the coefficient of static friction (0.1) and all the other variables, how do I verify that no slip occurs?
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### How does friction affect the motion of a pendulum?

I would like to know what is the difference in the equation of motion of a pendulum in the presence or the absence of frictional forces. And how this translates to the solution of those equations?
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### Sliding blocks problem

My first post here, so I apologize if this is duplicated elsewhere. It IS a "homework" problem, but it's public domain, a posted exam with answers... http://www.mun.ca/physics/undergraduates/...
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### Energy taken to move volume of blood through a blood vessel

I am trying to find simple ways to get rough answers to how much energy it would take for a unit volume of blood to move along a blood vessels. My main aim is to compare energies it would take for a ...
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### Friction Resulting from Differing Masses

A friend and I are curious about something. We created a ramp from some wood (like a skate ramp) that's not purely circular in nature. We did so with the intent to test how the mass of an object can ...
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### How can the work done by friction be positive? [closed]

I have this energy related problem that i cannot understand in this problem, I am required to find the velocity of the 4.8kg mass when it hits the ground. I easily solved this problem using newton's ...
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### Frictional Force of a Rolling Object

I'm not sure that I understand this problem: A spool of wire of mass 4.7kg and radius 0.99m is unwound under a constant wire tension 10N. Assume the spool is a uniform solid cylinder that rolls ...
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### Impulse Equations

A solid sphere of mass $m$ rolls without slipping on a horizontal surface and collides with a vertical wall, elastically. The coefficient of friction between the sphere and wall is $\mu$. After the ...
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### Increase in temperature of metal piece during filing explain by the Gibb's equation?

When we file the metal the surface of the metal gets worn out in the form of small pieces of metal. The file acts as medium to transpher the energy from the body to the metal piece in the form of work....
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### Lagrangian Mechanics + Account for friction of block

$\newcommand{\dd}{\mathrm{d}}$ I am trying to work out the Lagrangian mechanics for a pendulum problem in order to animate it. I'm working on one of the examples in the Wikipedia page on Lagrangian ...
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### An object is accelerating on a rough surface with frictional force of 10N. Is the friction doing any work on the object?

This question might look stupid to some but I am in great confusion. An object, say a box, is moving on a surface with some velocity v and is accelerating. It means that the force applied by the box ...
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### Is air friction active force or constraint force?

Can air be regarded as a constraint body when a rigid body is moving? Or is the moving itself cause the friction so it is an active force?
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### Power and friction [closed]

An object moves with a constant velocity of 10m/s on a rough surface with frictional force of 50N. What is the power of the object? And why do we use force of friction instead of the force provided by ...
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### Interpreting force components in statics problems involving inclined planes or similar

I'm having troubles to understand how to interpret the components of forces on inclined plane in quite complicated situations. I will make an example of one of the cases where I get confused. ...
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### Three-log problem [closed]

Three uniform round rigid cylindrical logs of the same size and weight are placed on a horizontal plane. The two at the bottom are touching each other, the third one is placed on the top as shown in ...