Physics AP help (a new question now)

[johnjohn320]

OK, I managed to figure out the first question. Rather than start a new thread, here's another problem:


http://pics.bbzzdd.com/users/johnjohn/no19.JPG
Basically, a pepple is whirled overhead in a circle, released at a theta and hits a target on the same plane as the circle but outside of it (from P to Q). The theta is suposed to be on the right side there (the symbol got cut off), and that's what I need to find. Everything else in my sketch is either figured out or given. I made a triangle out of it as shown, and am figuring that if I can find the middle angle, I can find theta.

But, since I can't assume that I've made a right triangle, I don't know how to find anything! Help!

Edit, I found a solution to it, and they put the right angle at the right side of the triangle. Where did that come from, how did they know that that was 90?

 

[cheapgoose]

i could be wrong but there shouldn't be a normal force, the seat isn't touching the ground right?

so you have mg, then tension.

so use the angle to find tension.

not sure what to do next, maybe find the acceleration, f = ma, then use a to find v. i think it's v^2/ r = a

 

[MrDudeMan]

its called a free body diagram, not a force diagram.

 

[johnjohn320]

oh duh, i got it right before i read your post. Not too bright of me. got it now, thanks!

 

[Gibson486]

its called a free body diagram, not a force diagram.

???? how does that help ?????

 

[johnjohn320]

bump for the new problem

 

[TuxDave]

Let me include some notation. Let me call the center of the circle O.

So the angle of corner QPO has to be 90 degrees. When things are moving in uniform circular motion, its velocity is tangent to the circle or in other words, it's perpendicular to the line that connects IT and the center of the circle.

 

[enjoi]

omg i did the same problem like two weeks ago... but i'm too lazy to forge through my crap and find the work, and i forgot how to do it :/

 

[MrDudeMan]

Originally posted by: Gibson486

its called a free body diagram, not a force diagram.

???? how does that help ?????

and i assume your response was more helpful? at least mine had to do with physics! get lost lamer