Friction Question (1 Viewer)

Drongoski

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(23 x 10 - P sin(30)) x 0.4 = P cos(30)

The Normal Reaction 'N' is not 23 x 10, but reduced by P sin 30


.: 23 x 10 x 0.4 - 0.4 x P x sin 30 = P x cos 30

.: P = (0.4 x 230)/(0.4 sin30 + cos 30) = 86.30188 ... Newtons

The basic idea is: Friction = Coefficient of Friction x Normal Reaction
 
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D94

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Not mine ->
Just want to say that this is an absolutely disgusting way of solving a basic friction question. It's not intuitive and doesn't assist struggling students in demonstrating what is going on.

I can provide another method if needed (basically what Drongoski has above with a FBD).
 

mandog97

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Just want to say that this is an absolutely disgusting way of solving a basic friction question. It's not intuitive and doesn't assist struggling students in demonstrating what is going on.

I can provide another method if needed (basically what Drongoski has above with a FBD).
Yeah I never do that. Could you show me your way of doing it? Thanks
 

keepLooking

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Just want to say that this is an absolutely disgusting way of solving a basic friction question. It's not intuitive and doesn't assist struggling students in demonstrating what is going on.

I can provide another method if needed (basically what Drongoski has above with a FBD).
It isn't my method and I surely haven't found a method that is considered more intuitive, I would appreciate if you could provide another method!
 

mandog97

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It isn't my method and I surely haven't found a method that is considered more intuitive, I would appreciate if you could provide another method!
I got it. Do you have a copy of Copeland (pg. 94/95)? It goes through friction questions really well, particularly this type.
 

Drongoski

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There is nothing to it:

The block moves when the horizontal component of P (i.e. P x cos 30) exceeds the maximum friction (= the normal reaction x coeff of friction}; about to slide when the two are equal. This latter was what my original post expressed.
 

D94

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Yeah I never do that. Could you show me your way of doing it? Thanks
It isn't my method and I surely haven't found a method that is considered more intuitive, I would appreciate if you could provide another method!
I know it's not your method, I even quoted the part where you said that.

It's how you set up the solution that makes it more intuitive, not the actual solution itself. A basic Free Body Diagram will make all the difference: http://puu.sh/kj2Us/afec99c63e.png
 

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