Recent content by willem2

  1. W

    Capacitor charge time, two conflicting answers

    The answers are the same. both give t = C*V/I. I don't understand what the problem is
  2. W

    B Six Pencil Puzzle

    Here are 2 solutions with 7 infinite cylinders. https://www.sciencedirect.com/science/article/pii/S0925772114000819 Major computation is needed to find solutions of 20 non-linear equations with 20 variables. The only thing in that article that's easy, is that if you have 2 parallel infinite...
  3. W

    Conflicting definitions of linear independence

    (3) is obviously not true. According to your definition no set of 3 vectors with 4 components can be linearly independent.
  4. W

    Conflicting definitions of linear independence

    A set of vectors is linearly dependent if it contains the zero vector, or if you can produce the zero vector by making linear combinations of the vectors. A zero column only implies that you can produce a zero row if the dimension of the vector space (number of elements) is equal to the number...
  5. W

    Intersection of a circle and a sine curve

    You didn't try to move the circle. The problem statement doesn't forbid this.
  6. W

    B Rainbow light reflection on TV from my hand

    But here the tv screen here is not tilted. Guessing a distance from the screen of 1m, the distance to the first maximum of 0.05 m and light with a wavelength of 600 nm, You need 83 pixels/mm. I think mobile phones come close to that nowadays. Of course we also need the size of the monitor...
  7. W

    I Energy Released From Dropping Things Onto Neutron Stars

    Yet, the golf ball won't deform very little, during the time it falls. The acceleration of the tidal force is only 400000/0.045 = (0.045 kg golf ball) = 8.9 * 10 6 ms -2 (1/2)at2 = 0.01 mm.
  8. W

    Solve for all angles x: cos(2x) + cos(x) = 0, where 0<x<2pi

    Actually, this can be done without quadratic equations. If you get your equation in the form: cos(a) = cos(b), you can conclude a = b+2k pi or a = -b +2kpi. no double angle formula's or quadratic equations required.
  9. W

    B I need help understanding the derivation of this 'Absolute Scale of Temperature'

    This is just Charles law (V/T is onstant at constant pressure), with T expressed in degrees Celsius, so you get (T+273.15) in the expression, instead of t
  10. W

    Circuit with potential difference across battery being zero?

    I don't know why you think this will happen? This depends on the exact battery chemistry, but at least with rechargeable batteries, this will charge the battery with the lower electromotive force, and it will raise its emf until the emfs of the batteries are the same. If R is large enough, this...
  11. W

    Python Who can find the largest prime number with their own programmed code?

    The best known way to find large primes is the lucas-lehmer test for mersenne primes (primes of the form 2^p-1 where p is a prime). This is actually quite simple to do # returns True if 2**p -1 is a mersenne prime, false otherwise # assumes p is prime def is_mersenneprime(p): if p==2...
  12. W

    Challenge: Find the minimum amount of draws possible for a list of integers

    We need some examples here. what happens if 2a becomes greater thant b-a, do you then exchange an and b? i don't see when a pair draws. It does seem like the computation of does_draw() is the problem. You could use a table or the @cache function decorator to not compute this function over...
  13. W

    Engineering Ordinary Diferential Equations in electric circuit

    This is a calculation of the impulse response of a second order linear system (mass - spring - damper). Are you allowed to use the Dirac delta function? in that case the right side of the differential equation is just δ(t), and you can use the laplace transform. A an equation with f(V'', V', v)...
  14. W

    Understanding a C64 program on the melody of a song as math equations

    No these are the correct notes, starting with the last beat of measure 32. On measures 17-32 the shift register is reset every beat of the kick drum, and the last beat of measure 32 is the last time this happens. I've noticed the following looking at this shift register. - A bit shift register...
  15. W

    Understanding a C64 program on the melody of a song as math equations

    No, the frequency values for A and B are 16*256 and 18 * 256, so the ratio between them is 9/8 = 1.125, the exact ration for a whole tone in just intonation. On an equal tempered piano that ratio would be 2^(2/12) = 1.1224... You probably can't hear the difference of 0.23% between those. The...
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