The resistance a surface or object encounters when moving over another.
Questions tagged [friction]
2885 questions
310
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2 answers
Why do ballpoint pens write better on pages that have pages below them?
If I write on the starting page of a notebook, it will write well. But when there are few or no pages below the page where I am writing, the pen will not write well. Why does this happen?
Ram Keswani
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254
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8 answers
How do towels stay on hooks?
Towels (and coats) are often stored on hooks, like this: To the untrained eye, it looks like the towel will slide off from its own weight. The hook usually angles upwards slightly, but a towel does not have any "handle" to string around and hang on…
Caleb Stanford
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143
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What does it mean for two objects to "touch"?
If you've ever been annoyingly poked by a geek, you might be familiar with the semi-nerdy obnoxious response of "I'm not actually touching you! The electrons in the atoms of my skin are just getting really close to yours!" Expanding on this a little…
Thomas
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109
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Why is oil a better lubricant than water?
How come mineral oil is a better lubricant than water, even though water has a lower viscosity? When two surfaces slide over each other with a gap filled with a fluid, the different layers of the fluid are dragged at different speeds. The very top…
DK2AX
- 4,860
76
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3 answers
Is there 'friction' in spacetime?
So, if all the bodies are embedded in space-time and moves through it, is there some kind of 'friction' with space time of the planets? For example, the Earth suffers friction when moving near the sun due the curvature and General Relativity and…
Jose Javier Garcia
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68
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What explanations are there for a rug steadily creeping at about a millimeter/day rate across a room?
I have bought a handmade rug of size 1.5 $\times$ 2m. About 1-2 weeks ago I noticed the rug was not in the center of my room and it had moved a bit. I thought maybe because I walked on it, it has moved. I put it in its place and it happened again…
Joe
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60
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6 answers
Can a Skydiver Land On a Large Slide and Survive?
Please forgive my lack of artistic ability, but here's my question: Consider that a skydiver, without using his parachute, were to fall exactly parallel to a giant curved slide that starts at $90\,^\circ$ perpendicular to the ground and gradually…
MegaMark
- 706
58
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2 answers
Why is the equation for friction so simple?
The general equation for the force of friction (static or kinetic) is $F_f = \mu * F_N$, where $F_f$ is the force of friction and $\mu$ is the coefficient of friction (its value is dependent upon the surfaces interacting on each other). Why is it…
user1546859
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47
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9 answers
What will happen to a ball kept on a frictionless inclined plane?
I was wondering about this question since I learned about rolling motion in the chapter on rotational mechanics. I was unable to come to a solid conclusion due to the reasons mentioned below. The following diagram shows a ball on a frictionless…
Vishnu
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47
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1 answer
Why are dishwasher washed glasses "squeaky clean"?
They seem to have increased friction after going through a dishwasher. The unpleasant (to me) squeaky feel is probably slip-stick friction exciting resonance in the glassware. But why? What has happened to the surface of the glass to make it like…
user56903
40
votes
6 answers
How can the Earth keep spinning with a liquid core?
In regards to the 'conservation of angular momentum' being the explanation of why celestial objects spin... If you fill a ball or any other container with a liquid and try to spin it, you will not see any more than 5 or 6 revolutions because of the…
user50507
- 409
39
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9 answers
Why do bikes hardly ever skid while braking with the front wheel?
When abruptly braking with the rear wheel on a bike, it tends to skid pretty easily. Doing the same with the front wheel is a very different experience. Instead of skidding, the bike lifts the rear wheel. I've never seen the front wheel of a bike…
Tiago Marinho
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37
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9 answers
Why do disk brakes generate "more stopping power" than rim brakes?
Bicycle's brakes generally fall into two broad categories: rim brakes where the braking pads pinch against the wheel's rim, and disk brakes where the pads press against a disk (rotor) that is rigidly attached to the wheel's hub. General wisdom is…
Kevin Kostlan
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36
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3 answers
Lagrangian and Hamiltonian EOM with dissipative force
I am trying to write the Lagrangian and Hamiltonian for the forced Harmonic oscillator before quantizing it to get to the quantum picture. For EOM $$m\ddot{q}+\beta\dot{q}+kq=f(t),$$ I write the Lagrangian $$…
user56199
35
votes
8 answers
Why does twisting a cork make it easier to remove from a bottle?
When we want to remove a cork from a bottle first we turn the cork. Turning in one direction makes it easier to remove in the axial direction. Does anyone know something more about this?