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  1. B

    Energy Problem

    Ok, this makes sense. So, I can have a separate Ug = 0 point for each element in the system?
  2. B

    Energy Problem

    1.24 m/s is correct.
  3. B

    What is the RATE of Rotation! help

    "0.65m diamter", you are correct.
  4. B

    Energy Problem

    I can't comment on your sanity :rolleyes: , but that goes back to my problem... How can it be 20 cm for the hanging block if Ug is not 0 at the point we would expect?
  5. B

    Energy Problem

    \Delta U_{g} = (m_{2}sin\theta-m_{1})gx \Delta U_{g} = [20.0 kg sin40 - 30.0 kg](9.80)(0.200) = -33.6 N
  6. B

    What is the RATE of Rotation! help

    (2.53 x 60) / (2 * pi * .65) = 37.1688006 I think you're forgetting r.
  7. B

    Energy Problem

    A 20.0 kg block is connected to a 30.0 kg block by a string that passes over a light frictionless pulley. The 30.0 kg block is connected to a spring that has negligible mass and a force constant of 250 N/m, as shown in the figure. The spring is unstretched when the system is as shown...
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    Normal Force

    Yes, and it/they were getting complex, so I wanted to get some feedback. I came up with the force exerted down on the chair as having an x component and a y component (different from what I posted). From there I was thinking I could apply that vector to the FBD of the chair and come up with my...
  9. B

    Normal Force

    I'm trying to think up situations that will help me understand more complicated situations... Let's say I have: a box on a slanted slope on a chair on the floor The floor exerts a normal force on the chair. But, equal to what? is it: a box m_{1}gcos\theta on a slanted slope m_{2}g on a...
  10. B

    Vertical Circular Motion

    I have a question: If R were to drop to zero, the coaster would fall, right? So, for v=9.9 m/s, it would actually lose contact with the track and fall. But for any value even minutely larger than R=0 (and thus v=9.9 m/s) the coaster would just barely "stick" to the track? Even for a super...
  11. B

    Newton's Laws and Friction Applied to Blocks

    I didn't mean to give the impression that I thought it was easy. I felt stupid because I made algebraic mistakes that I shouldn't have made. After spending so much time on the problem, I guess I was getting used to the "situation" in the problem... Thanks again.
  12. B

    Newton's Laws and Friction Applied to Blocks

    Thanks! I got it. Boy, do I feel stupid. I think it looks ok, now, right? (this isn't homework, btw, it's just extra practice) I made 2 algebraic errors: 1) when I pulled out the N, I didn't change the - to a + 2) when I divided by m, I didn't divide Q by m I found them while...
  13. B

    Newton's Laws and Friction Applied to Blocks

    Thanks for the help. I tried the problem over again using ma=Q/2 and was able to easily solve both (a) and (b). FYI The correct answer is listed as having the cos and sin reversed from what you said... I'm a bit concerned though... I was shown how to do part (a) as follows: Find amax for...
  14. B

    Falling Laundry

    Dorothy and Doc Al, Thanks for the replies. My original reply was lost... Question: For UCM problems like this in general, is it generally safe to ignore forces that would act in the tangential direction? (in this case mg*cos(theta)) Thanks again!
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    Newton's Laws and Friction Applied to Blocks

    Given: 2 wedge shaped blocks arranged as a rectangle. The bottom block is on a frictionless horizontal surface. Horizontal force Q is applied to the vertical side of the bottom block. Find Q max, the maximum value of Q where there is no slipping, in terms of us, m, and theta. Masses: m and m...
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    Lost Post

    I posted a reply in a thread (Falling Laundry) a couple of hours ago and now it's gone. Is this related to the server move? Should I just repost the reply?
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    Falling Laundry

    I have a couple of questions for this problem, so I figured I'd post them here. I've spent a week on this, and have been through several books, so it's not due to a lack of effort. 1.) The normal force exerted on the laundry, the centripetal acceleration, and the component of gravity that...
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