Statics: Incline plane an friction

by thspoq2
Tags: friction, incline, plane, statics
 P: 17 Ive been working on this problem for a little while now and basically, I dont know where to go. I have found the friction angle of 7 degrees but I really have no idea where to go next. My book doesnt have any examples like the problem. The problem looks alot like a basic physics problem so I pulled out my old physics work to see if there was an equation for it, no luck there. Anyways, any help would be much appreciated. Thanks I scanned the problem from my book. I also circled it (sorry about the marks on there, my eraser wasnt working too well):
 HW Helper P: 879 Forget about the angle of friction. Draw a free body diagram. You know that the friction force will be acting up the plane. That's one force. Resolve the weight of the block into components parallel to and perpindicular to the slope of the plane. That's two more forces. Ditto for the force P. The last two forces. In the case of limiting friction, the friction force will be just balanced by the total force acting down the plane.
 P: 246 Yep, resolving perpendicular and parralel gives 2 simulataneous equations which can be solved and plus one gets R which is needed to calculate Fr.
P: 17

Statics: Incline plane an friction

Thanks for the replies.

Im still not having any luck, I need a new major:(
 P: 17 Thanks for the replies. Im still not having any luck, I need a new major:(
 P: 17 whoa, I didnt mean to do that, sorry
 P: 246 Come on mate - cheer up its not that hard. Go to mathnet.net or mathnet.com (cannot remember which site it is) and look at M1 or M2 that is A-Level UK text books and has this exact statics stuff in - and its well explained on the site with examples. Any more help needed after that post again!! But remember Hasta La Victoria, Siempre
 P: 17 I went to both of those sites and I couldnt find the information. If someone could give me a visual process of what I have to do (equations etc), I can probably pick it up. Im a visual learner. I have to see the process done before I can repeat it.
 P: 17 Ok, I found the site and so far it has been helpfull..but, on one of there example problems, I dont see how they got a certain number. http://www.mathsnet.net/asa2/2004/m15exam5.html For step (a), could someone please explain to me how they are getting R = 117.7
 P: 246 IT shows steps if you click the applet button "steps"
 P: 17 I guess one of the reasons I havent been getting much feedback is because I havent been showing any work. Heres where im at now, sorry about the poor handwriting:
 Mentor P: 21,652 First, calculate the other force - the force normal to the plane, and with that, the friction force. Next, build some equations for what force "p" does - they'll look similar to what you did for the weight's components. You'll end up with two relevant forces due to the block's weight (normal and parallel to the plane) and two equations for the same two forces due to force "p". After that, you'll need to combine the equations you generate and solve them together with algebra. Hopefully when you see the equations, it'll be obvious how to combine them to make the variables drop out...
P: 17
 Quote by russ_watters First, calculate the other force - the force normal to the plane, and with that, the friction force. Next, build some equations for what force "p" does - they'll look similar to what you did for the weight's components. You'll end up with two relevant forces due to the block's weight (normal and parallel to the plane) and two equations for the same two forces due to force "p". After that, you'll need to combine the equations you generate and solve them together with algebra. Hopefully when you see the equations, it'll be obvious how to combine them to make the variables drop out...
I took your advice and this is where I got. The book gives an answere of 17.2 and im getting 16.3. What im a doing wrong?