# Questions tagged [friction]

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

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### What work, and why, is being done on this system of two rotating circular disks

A uniform circular disc with mass $m_1$ and radius $R_1$ is fixed at its midpoint and rotates at angular velocity $w_1$. Another uniform circular disc with mass $m_2$ and radius $r_2$ is carefully ...
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### Velocity and related frictional forces

I will illustrate my question using a simple example. Lets imagine the folowing situation: a big surface, a book on this surface and another smaller book located on the first one. There is friction ...
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### Friction during ball backspin and overspin

I already know sliding friction of ball on a flat table and rolling resistance of it. How do I know coefficient of friction value when the ball has backspin with some angular velocity $\omega$? And ...
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### Stopping a spinning object with a flexible gripper

I would like to know how deformation of the contact surface affects friction of a spinning object. In the image below I have a 2D problem of a spinning circle with two elastic "fingers" pinching it ...
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### Work done in equilibrium positions

I am confused in work done against friction. Let $F$ be the friction when a big stone is pushed by person on ground and $T$ be the component of force applied by a person in the direction of ...
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### Why did Galileo use a ramp instead of a rope/pulley in his famous experiment?

If I understand correctly, one can derive an equivalent relation between distance the body falls and time, by using a rope/pulley system too. Conceptually it may be easier and perhaps more natural. ...
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### Friction energy dissipation calculation

In a moving block, a variable force pushes it. Friction is acting against the movement. Below equation specify the amount of energy could be used to give motion: $$E_1 = \int F_T(t) .v(t) .dt$$ ...
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### Why is this system isolated (revised)?

(Image updated for clearance) Hello, Assuming that there is no friction anywhere and both box 1 and ramp 2 start at rest, I was wondering why this is an isolated system in terms of momentum ...
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### Directions of static & kinetic friction?

Static friction : Static friction opposes relative motion between two surfaces. The car is moving at some tangential velocity relative to the road. Thus, static friction should act in the opposite ...
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Suppose A motorcycle is coming down a slope. Only gravity is acting. If we put 2 wheels more in that motorcycle, will the speed increase or decrease compared to normal 2 wheels? If more wheels are ...
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### Will the hinge on a piece of wood affect the calculation for kinetic energy?

I was working on a problem of finding the kinetic that a point of a rectangular piece of wood will have after it swings and hits something. I have the following diagram: The rectangle has length $L$,...
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### How to calculate resisting torque due to moment of inertia

I'm trying to determine whether a motor is suitable for an experiment. I know the motor's torque and the moment of inertia of the disk it will be turning. I was able to find the angular acceleration. ...
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### Static friction free body diagram on a flat plane

Do you include static friction on a free body diagram for a static box on a flat surface? Or do you just include Force of gravity and Normal force? We know when the box is moving there is Frictional ...
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### When an object is moving, does air resistance build up after it begins to move or during?

For example,if a car is accelerating to 70km/h, when the car is at 35km/h, will air resistance also be at 35km/h or will it slowly build up after it begins accelerating?
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### Do nucleons experience friction?

I know that friction occurs because of imperfect surfaces rub against each other, and to my knowledge this occurs on the molecular level. However, since nucleons have spin, I was wondering if, since ...
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### Forces acting on an aircraft during landing

I am currently busy with a project which involves the design of a landing skid for an unmanned aerial vehicle. I am currently underway with calculating the forces which will act in on the landing skid ...
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### Confusion about work done by a force in different reference frames

Suppose I have a little mass m resting on a big slab mass M resting on a table. There is a frictional force between the little mass and the slab, but not between the slab and the table. Suppose I now ...
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### Conservation of linear momentum after explosion with friction

Let's say you have a bomb at rest submerged in a liquid. It then explodes into two equal fragments A and B which leave in opposite directions. If we ignore the fluid and any sound or light we can ...
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### 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 ...
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### What does the term “no slipping” mean in mechanics?

Say, I have two blocks. One block is on top of the other. Suppose friction is present everywhere. What is the condition for no slipping?
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### Mathematical Mechanics - Friction Question (weight is laid upon an inclined plane)

A weight W is laid upon a rough plane [µ=1/(sqrrt3)] inclined at 45 degrees to the horizon. It is connected by a string passing through a smooth ring A, at the top of the plane, with a weight P ...
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### Kinetic Versus Static Friction Problem

Block one is on top of block two, with blow two on a frictionless table. The system of blocks is accelerating to the right due to a force applied strictly to block one. What direction is the ...
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### What is the minimal friction force required in order for a ball on an incline to roll without slipping?

I read an article now and it confused me completely. Since I thought I have read somewhere else a completely different solution. You put a ball on an incline at rest. What is the minimal friction ...
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### Object falls off an inclined plane, what's the acceleration of the plane?

The problem statement is as following: "We have an object with mass m falling down, with friction, on the bigger object with mass M and tilted with the angle alpha. If the bigger object is moving ...