Search results

  1. D

    Strength of Materials- Asymmetric, simply supported beam problem

    I'm working on a problem but I've hit a road block.. Then the cross section of the piece is here: The first part of the problem is to determine Iy, Iz, and Iyz of the member.. I found the y value of the centroid to be 2.8587" and the z value of the centroid to be 1.0734" using the...
  2. D

    IVP and Existence/Uniqueness Problems

    when doing these, am I just concerned with x and x' at the specified points? Would I just plug 5 in where there's an x and 2 when there's an x'? I have no clue how to solve these.. There's no answer key and this is one of the few topics he didn't include an example problem in the book for. Am I...
  3. D

    IVP and Existence/Uniqueness Problems

    I'm working on a problem for my diffEQ's class. It reads: For each of the given initial value problems, what is the region where the existence and uniqueness of the solution is guaranteed? Is it all t, or t > -3, or a neighborhood of t = 1? a) x'' = t x x' + sin(t) b) x'' = tx + 2x' +...
  4. D

    Powering a DC motor

    "err....if it's _really_ 2.5HP, that's about 2Kw of power or 16 amps at 120v...which is at the limit speced for the beefed-up version of the suggested "ck1400.htm" board. And, I might add, about 5 times the amps (and 30 times the power) of your usual laptop charger... Maybe it's .25 (1/4)HP...
  5. D

    Powering a DC motor

    The motor is a perm. magnet motor. When the treadmill was assembled, the mains went through at least a circuit board before getting to the motor. I'm still looking for a power supply.. I watched this http://www.youtube.com/watch?v=cyhzpFqXwdA&feature=related which helped a bit. If the results...
  6. D

    Powering a DC motor

    The laptop charger did not work. I hooked up the two cables from a cordless drill to the treadmill motor and it seems to work, rpm is dependent on trigger pull, etc.. However, powering a 2.5 horse motor with a small hand drill battery leaves something to be desired. Perhaps a better course of...
  7. D

    Powering a DC motor

    This is my understanding of it right now, whether it's right or wrong C = wall outlet B = laptop charger outputting 20 volts DC A = one of the output wires is split and some sort of variable resistor is placed there (preferably with a handy little twist knob lol) to control the speed of...
  8. D

    Powering a DC motor

    I've been looking into it before and after posting. What do you have to vary to get a DC motor to spin at a different speed? Would rpm from a 120 volt power supply be roughly double the rpm from a 60 volt power supply, or is it based on current? Edit: I have an old laptop charger that outputs...
  9. D

    Powering a DC motor

    Hey guys, I'm working on a project involving a DC motor. I'm in school for mechanical engineering.. Electrical problems haven't really interested me so this is the first I've ever really looked into it apart from studying basic circuits in a physics course last year. Anywho, the project: I...
  10. D

    Statics: Force on a member of a frame

    FBD of member CEF It just dawned on me that if the magnitude of Cx = Ex then the magnitude of Bx is also the same, right? So from there I could find the moment about A: (assuming clockwise is positive) MA = 0 = (100lbs)(24in) + (Bx)(12in) - (Cx)(18in) would then turn into 2400 + 12x - 18x...
  11. D

    Statics: Force on a member of a frame

    Homework Statement Determine the forces acting on member ABCD The 100 lb force acts horizontally at point D, the large, bold circle is a wheel, and the smaller, less bold circles indicate pins connecting the members. Member BE is solid. I forgot to label point F in the picture...
  12. D

    Comp Sci Fortran 77 reading from text file, printing

    i got it figured out, sorry :blushing: my friend told me to take out the "1x" from the format 100 and 110 statements, along with some other tweaks. does anyone know why taking "1x" out makes it work? heres my final program: c dorado29--COS215--3/30/11--Problem #7--Temp, Press, Vol, Time...
  13. D

    Comp Sci Fortran 77 reading from text file, printing

    Homework Statement Write a program that reads the time, temperature, pressure, and volume measurements from a data file like : 0900015001990700 1000019602210877 1100021202790925 1234034203221015 1300038803221121 1400044803241425 1503051303201520 1604055503181665 1700061303191865...
  14. D

    Focal length of mirror

    Homework Statement A 2.0 cm tall object is placed in front of a mirror. A 1.0 cm tall upright image is formed behind the mirror, 165 from the object Homework Equations 1/s + 1/s' = 1/focal length h' / h = magnification -s' / s = magnification h' / h = s' / s (i found this...
  15. D

    Find Acceleration of a sliding object

    Let's say two objects are dropped at the same time. One weighs 1kg and the other weighs 100kg and wind resistance isn't a factor. Which one hits the ground first? My point is: weight doesn't change how fast something accelerates towards the ground (unless friction is involved) you will only...
  16. D

    Tension of 2 cables supporting one object

    Homework Statement A 1,000kg steel beam is supported by 2 ropes. What is the tension in each? Rope 1 on the left is -20 degrees from vertical and rope 2 on the right is 30 degrees from vertical, making a V shape, the tops being connected to a ceiling. Homework Equations Not sure...
Top