# Tagged Questions

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

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### 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 ...
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### Does really a spring compresses placed between two blocks when one block is given force on a frictionless surface?

When Spring is placed between two bodies on a frictionless surface it gets compressed when one block is given kinetic energy as told by my physics teacher. But it should not compress as there's no ...
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### Friction between needle and bearing

I have a question about friction and its effect on materials. Please forgive my long description of the problem. I have made a Device that is designed to slowly oscillate a magnetically suspended ...
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### Calculating constant velocity from friction [closed]

I'm unsure if my Book is wrong. Either way, we send a pinball through a cylinder filled with oil, the forces that apply are. Fpinball = 15,8 ∙ 10^−6 ∙ 9,82 = 5,69 ∙ 10^−5N Foil = 𝜌 ∙ 𝑔 ∙ 𝑉 = ...
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### Does a car consume more fuel when it's raining?

Yesterday my wife asked me that question, and I couldn't answer. Consider a car, in a sunny day, and that is consumes x gallons per mile. Considering that everything is equal, except that it's ...
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### Heuristic equation for Friction force between materials

I'm programming a game where different types of objects will be sliding over different types of terrains (Top-down in two dimensions). At my current level of physics education we are given the ...
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### Finding the coefficient of friciton [closed]

I'm asked to find the coefficient of friction before the bar starts sliding. Here is my solution -> ∑M = 0 -mg * 1.4863 + 1.8159*T = 0 (T*1.8159) i found by using a cross product ( -2.9726i+ ...
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### How does magnetic field gets generated by friction between high temperature molten metallic cores?

I was watching "Strip the cosmos" show on Discovery science channel last day and they explained that earth produces magnetic field due to rubbing of the two concentric cores, both the molten metal ...
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### work done in observer frame

I had a few questions. 1) Is work done independent of the refrance frame? 2) Suppose a cart-A with rough surface is accelerating with an acceleration a and another cart-B with acceleration b. Now to ...
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### Must one include friction and gravitational force in the work term?

Example problem: "A sled has an initial velocity up a ramp of 5 m/s, the ramp has an angle of 20 degrees to the horizontal, and the coefficient of dynamic friction between the sled and the plane ...
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### Accelerated pure rolling and friction

I know that if a body is pure rolling with no acceleration then friction acting on it is zero. But what about if the CM has an acceleration? Then can we say that friction is present? Suppose that ...
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### 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 ...
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### 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 ...
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### Determining direction of static friction when tension and gravity are present

I'm a private Physics tutor, and I'm a bit stumped by one of my student's problems. It's #3 on this worksheet (http://www.hopewell.k12.pa.us/Downloads/Inclined%20Plane%20Worksheet.pdf -- not his ...
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### Angle of repose for cylinders and spheres

Is angle of repose of a cylinder or a sphere same as angle of repose of a block on an rough incline? How to calculate it for spheres and cylinders?
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### Mismatch between underdamped and critically damped solutions

If you have a harmonic oscillator with damping $D$ (e.g. small angle pendulum) $$\ddot{\theta}+D\dot{\theta} + \theta=0$$ then the solution I get in the underdamped case ($D^2-4<0$) is: ...
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### Why friction between two smooth surfaces is high? [duplicate]

If we place two smooth surface one over the other why friction increases or becomes high ?
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### 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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### Finding the friction before slipping [closed]

There is a string that is attached to a bar as shown below in the picture. What is the coefficient friction between the bar and floor before bar starts slipping. I have chosen a pivot point about ...
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### 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 ...
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### 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 do objects move when you apply a force that's equal in magnitude to the friction? [duplicate]

If the friction on an object is 200 N and you apply 200 N, it seems, the forces should immediately cancel each other out since the friction and your applied force go in opposite directions, leaving ...
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### Center of mass chaotic in n-body gravitational interactions?

I wrote a gravitational particle simulation. To prevent the particles flinging off out of the screen, I added a bit of friction (it also makes the animation prettier as particles spiral into one ...
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### Why does friction play the role of centripetal force during the turning of a car?

What makes frictional force the centripetal force of a car turning along a curve? As friction is the opposing force and acts anti-parallel so there is no component of frictional force towards the ...
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### How is direction of static friction not opposite in direction but perpendicular when dealing with centripetal forces?

I was trying to wrap my head around this solution, and the whole idea of a car moving around a level curve, how the friction supplies the centripetal force. But I still can't wrap my head around the ...
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### Why does chalk dust stick to a chalkboard?

I understand that friction causes the chaos dust to come off the stick of chalk, but what exactly is causing the chalk dust to stay on the chalk board until rubbed off?
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### 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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### If the friction coefficients depend on the object's property, why do they change in sliding & rolling, despite the object being same? [duplicate]

I know that when you roll an object instead of sliding it reduces the friction you can easily move an object. Consider the object to have a weight $W$ on a horizontal surface and the two objects have ...
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### Perturbation Method in Mechanics: Average velocity of a small mass on a vibrating inclined plane [closed]

I've stumbled across this delightful and difficult collection of problems, by Jaan Kalda. The following problem has stumped me. (It's probem 16 on the sheet, which I have provided as a link) ...
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### force required to move a object in slope with rolling tyres [duplicate]

Consider a object of 5 kilos which is fixed with 4 rolling tyres (like in a trolly) which is in a slanting position of 30 degree angle. My question:How to find the force required to move the object ...
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### Does friction depend on the direction of motion?

In my experiment of finding the moment of inertia of a flywheel, I first rotate the flywheel in the anticlockwise direction and then in the clockwise direction, but I am getting different values of ...
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### Intuition for why friction on rolling objects is in the same direction as motion?

When we usually draw friction, it is opposite the direction of motion. However, in rotational motion problem when a cylinder is rolling on the floor, it is in the same direction as the motion. I did ...
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### 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 ...
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### treadmill physics, wheel size vs. counterforce

I'm trying to design a classical treadmill for rodents which has two wheels at the two end and a plain "conveyor" belt in between. What is the best way of designing this if i want to have minimal ...
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### Force of an object “skidding”?

Let's say I put the brakes on really suddenly in a car that was moving at 40mph. If I know how much force it takes to break the adhesion of the wheels, how do I find the force the car is exerting? ...
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### 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 ...
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### Gravitational Force [closed]

If energy is represented by Acceleration=A, then am=F ams=W (ams)/t=P Acceleration is always present when motion is present, acceleration is the energy. Since gravity translates into ...