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What's everyone up to right now?
RE: What's everyone up to right now?
(January 11, 2017 at 3:12 pm)Alex K Wrote:
(January 11, 2017 at 2:19 pm)SteelCurtain Wrote: Um... if it were placed on its side, what mass of a cube with a µ of 0.35 would remain static?

Well, that's a trick question right?. If it's standard static friction, the mass cancels out because it multiplies both the friction force which is proportional to the normal force, and the downhill force.

Maybe I worded it poorly. If the shelf were placed on it's side making the surface angle approximately 20° to horizontal. A wooden block is placed at the on the higher end of the surface. What is the largest mass possible so that the block doesn't slide if the coefficient of friction between the block and the shelf is 0.35?

I distinctly remember problems like this in statics. It may have been dynamics, because it involves movement, but I remember using µ in statics, too.
"There remain four irreducible objections to religious faith: that it wholly misrepresents the origins of man and the cosmos, that because of this original error it manages to combine the maximum servility with the maximum of solipsism, that it is both the result and the cause of dangerous sexual repression, and that it is ultimately grounded on wish-thinking." ~Christopher Hitchens, god is not Great

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RE: What's everyone up to right now?
Watching news flash regarding Chargers.
"For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring." - Carl Sagan
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RE: What's everyone up to right now?
(January 11, 2017 at 2:33 am)pocaracas Wrote:
(January 11, 2017 at 2:01 am)Cthulhu Dreaming Wrote: So we just hit the 6" of snow predicted - and it's supposed to snow for 12-15 more hours.

Oh fuck oh dear.

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Officially, we got 12" but it started again this afternoon. Didn't make it to work despite best effort. They'll survive.
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RE: What's everyone up to right now?
Preparing to turn in for the night.
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RE: What's everyone up to right now?
at my grandma's, looking at the nile river from the balcony, listening to music, smoking.
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RE: What's everyone up to right now?
(January 11, 2017 at 5:56 pm)SteelCurtain Wrote:
(January 11, 2017 at 3:12 pm)Alex K Wrote: Well, that's a trick question right?. If it's standard static friction, the mass cancels out because it multiplies both the friction force which is proportional to the normal force, and the downhill force.

Maybe I worded it poorly. If the shelf were placed on it's side making the surface angle approximately 20° to horizontal. A wooden block is placed at the on the higher end of the surface. What is the largest mass possible so that the block doesn't slide if the coefficient of friction between the block and the shelf is 0.35?

I distinctly remember problems like this in statics. It may have been dynamics, because it involves movement, but I remember using µ in statics, too.

I'll give you the calculation to show you what I mean - so in that case the force driving the block downhill is m*g*Sin(20)=0.342*m*g. We have to compare that to the maximum force of friction which I assume is given by µ * the normal force pressing the mass onto the surface, which is given by m*g*Cos(20), so the max. force of friction is µ*m*g*Cos(20)=0.35*0.94*m*g=0.329*m*g. Both this and the downhill force have a factor of m, so it cancels out, and the block will slide down the incline no matter what the mass because 0.342 > 0.329
The fool hath said in his heart, There is a God. They are corrupt, they have done abominable works, there is none that doeth good.
Psalm 14, KJV revised edition

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RE: What's everyone up to right now?
Getting beaten up by Emma.
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RE: What's everyone up to right now?
(January 12, 2017 at 5:05 am)robvalue Wrote: Getting beaten up by Emma.

What did you do now, Rob?
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RE: What's everyone up to right now?
I was in the same room as her Huh
Feel free to send me a private message.
Please visit my website here! It's got lots of information about atheism/theism and support for new atheists.

Index of useful threads and discussions
Index of my best videos
Quickstart guide to the forum
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RE: What's everyone up to right now?
So this is pretty cool: I got a Facebook message from an editor-in-chief of a small pop culture news site asking if I'd like to become a writer for them. He came across my profile on Quora, where one of my answers has gained about 45,000 views and counting.
It's a non-paying role, but they're hoping to expand and eventually start generating ad revenue, so there might be some coin in it for me down the line. Either way, it's a nice chance to hone my writing and apply it to something semi-practical Big Grin
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