Recent content by Darkalyan

Homework Statement This isn't a homework question, but more like a theory question that my teacher and I are having trouble figuring out. We're trying to figure out why this ball, more or less, stays still in a high speed stream of air: http://laserpablo.com/videos/videofiles/Bernoulli.htm...

Hmm. Could I take the center of mass of the entire circle, assuming there's no cut outs. Then I take the center of mass of the cut-outs, and pretend they act like 'negative' masses, so instead of having the centerr of mass of the composite system get closer to them, they are farther away? So...

Homework Statement http://docs.google.com/Doc?id=d277r7r_60c2235gfg Homework Equations M(Rcm)=\int(rdm) The Attempt at a Solution Okay, so I've figured out that I have to integrate the radii by the mass element dm, which in this case would be p, because that's the mass/unit area? I think...

oooh. didn't catch that. thank you. so then i just add a m to the left side of the equation, which makes the m's cancel out, and the final answer is theta=arcos(-g/(Rw^2)) Is that right now?

Homework Statement http://docs.google.com/Doc?id=d277r7r_58d3chgqfj Homework Equations a=w^2*r The Attempt at a Solution a=w^2*r w^2*r*cos(theta)=-mg theta=arcos(-mg/(Rw^2)) I'm pretty sure that's right, because the vertical component of the acceleration has to equal the...

Okay, that was some really amazing help you've given me. I just wanted to thank you for being such ana wesome tutor. You were so totally insanely useful, it was amazing. I am so happy I've found this website, and I am SO becoming a physics major when in college.

Aaaah! Thank you so much, that last post, for some reason, really cleared up things for me. So, the force has 2 components, horizontal and vertical, but there's really only 1 moment. However, the moment of the vertical component is 0 (about the other hinge) because there's no lever arm. Thus...

Hm, I think I get it. So, I get the moment of the weight about a hinge is the weight times the horizontal distance. It's kind of like how torque is force times lever arm, but in this case the lever arm is just the horizontal distance to the weight. I understand the vertical component of one...

Ugh. I still don't get what exactly a moment of force is, so I'm going to try another way, okay? :(. Okay, so I got the horizontal forces is F * (L-2d) = Mg(W/2), and the force is the same for both the upper and lower hinge, just opposite in direction. For the upper hinge, the force is towards...

Okay, I'm still a little confused about what exactly a moment of force is. So, for example, the top hinge. The moment of force in the y diriection would be MG*(W/2), correct? And, in the X direction, there is no moment of force because there is no force in the X direction. Do I have the right...

Hm, okay. When you say take 'moments' about the point for one of them, should I take the moment of inertia of the door about one of the hinges, using the CM as the door? Or, should I take the angular momentum of the door? But, the angular momentum is 0 because the door doesn't move, so I'm not...

Homework Statement http://docs.google.com/Doc?id=d277r7r_56tbhcw4cf The Attempt at a Solution So, I don't know how to draw this out by hand, so I'll explain what I thought I should do. I thought I'd pretend the door was only at its center of mass, making it a point particle. Then, I...

Sorry, I'm kind of lazy when it comes to simplification, so that's why I thought it was a 'lot' of algebra :). Thank you very, very much for your help.

Hmm. Okay. So, if there's rolling w/out slipping, then v=wR. I then plugged that into the fact that -Mgh=½Mv² + ½Iω², and plugged into the w (that w=v/R). I did a bunch of algebra, and got that v=sqrt(-4gh/3), which works out to be a positive # b/c h is defined to be a negative distance fallen...

Okay, so I know that I=(MR^2)/2, but you said that w is related to v. I don't see the relation?