Repose Angle: Why Doesn't Matter Float?

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39 replies · 6K views
Not with the constant velocity but with acceleration. Youuuuuuuuu can calculate it.
 
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Doc Al said:
Start with the mass resting on the incline at some angle less than the limiting angle. Slowly increase the angle, until it just starts to move. When it starts sliding, kinetic friction (which is generally less than the static friction) takes over and there is a net force downward.


you say the body will have net force downward then it'll accelerate which contradicts the fact that it moves down with CONSTANT SPEED which cannot happen if net force ACTS.
 
mukundpa said:
Not with the constant velocity but with acceleration. Youuuuuuuuu can calculate it.

this case can be thought to be similar to the body on a horizontal plane.
there when force just equal to the static force is applied the body starts moving but with zero acceleration
 
Nirav Chavda said:
let me make it clear for you... THE BODY IS OBSERVED TO MOVE DOWNWARDS WITH CONSTANT VELOCITY-- THATS A FACT not my THOUGHT .
Have you seen this "fact" with your own eyes? Do you have a reference?

I'm doing the "experiment" right now in my office, with an eraser and a clipboard. Sure looks like accelerated motion to me. :wink:

Of course, if you are able to keep the speed very small (with tiny adjustments of angle), it would not surprise me to see the friction changing back and forth from static to kinetic. (The typical models of friction are only approximate.)
 
Nirav Chavda said:
this case can be thought to be similar to the body on a horizontal plane.
there when force just equal to the static force is applied the body starts moving but with zero acceleration
How do you start moving with zero acceleration?
 
Doc Al said:
How do you start moving with zero acceleration?

brother .. you've got an excellent point there but I'm still uncontent. i'll try get to the main core just wait..
 
thank you very much you've solved my problem.
the simple answer to this was that the body will accelerate down due to some smallest inevitable disturbance(at quantum level) and this would change the Static F. to kinetic F. which is lesser. and so new net force acting downwards will be produced resulting in downward motion.

thankyou again for spending your working :wink: hours for helping me out!
meet you at some other forum!
 
I am also having difficultly following the question. If the object is initially not moving how can it be also moveing at a constant speed? Speed is 0. How can it be on a frictionless incline (mentioned air frictionless) and be suspended? I need help in visuallizing this. Sorry
 
Nirav Chavda said:
the simple answer to this was that the body will accelerate down due to some smallest inevitable disturbance(at quantum level) and this would change the Static F. to kinetic F. which is lesser. and so new net force acting downwards will be produced resulting in downward motion.

Oy vey!

And all you foolish people thought quantum effects cannot manifest themselves clearly at the macroscopic level!

Zz.
 
Oy vey! This has got to be one of the most innane threads I've ever seen here - and this from a guy who put a lot of energy into a 9/11 conspiracy thread! I'm sooo glad I didn't see this thread this morning.

Silly ZZ - statements of facts are things I make and you accept...