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Homework Help: Derivations of SI Units in my High-School Physics formulas.

  1. Apr 15, 2007 #1
    I was bored so I make fun with derivations of SI units of many Physics formulas.
    Note, this should just be called "introductory physics", that means NO calculus (but rate of change designated by the delta symbol) and motion is in one or two directions only.
    This is high school physics level in Australia only (State NSW to be more precise).

    Here goes, I hope I'm right.

    f = 1/t

    Unit: Hz (Hertz)
    Derived Unit(s): s-1 (per second)

    W = Fs

    Unit: J (Joule)
    Derived Unit(s): N m (Newton-metre)
    Further Derived Unit(s): kg m s-2 x m = kg m2 s-2 (kilogram-metre squared per second squared)

    (N = kg m s-2)

    q = I/t (I = q/t)

    Unit: C (Coulomb)
    Derived Unit(s): A s (Ampere-second)

    (A = C s-1)

    R = V/I [V = IR (Ohm's Law)]

    Unit: Ω (Ohm)
    Derived Unit(s): V A-1 (Volts per ampere)
    Further Derived Unit(s): kg m2 s-3 A-1 x A-1 = kg m2 A-2 s-3 (kilogram-metre squared per Ampere squared-second cubed)

    (V = kg m2 s-3 A-1)

    V = E/q (V = ΔPE/q)

    Unit: V [Voltage (Potential Difference or Electromotive force (emf))]
    Derived Unit(s): J C-1
    Further Derived Unit(s): kg m2 s-2 x A-1 s-1 = kg m2 A-1 s-3 (kilogram-metre squared per Ampere-second cubed)

    (J = kg m2 s-2 & C = A s)

    P = E/t

    Unit: W (Watt)
    Derived Unit(s): J s-1 (Joules per second)
    Further Derived Unit(s): kg m2 s-2 x s-1 = kg m2 s-3

    (J = kg m2 s-2)

    F = ma (Newton's Second Law)

    Unit: N (Newton)
    Derived Unit(s): kg m s-2 (kilogram-metre per second squared)

    (a = m s-2 = N kg-1)

    B = F / LI (F = LIB)

    Unit: T (Testla)
    Derived Unit(s): N m-1 A-1 (Newton per metre-Ampere)
    Further Derived Unit(s): kg m s-2 x m-1 x A-1 = kg A-1 s-2 (kilogram per Ampere-second squared)

    (N = kg m s-2)


    Wb m-2 (Weber per metre squared)

    Ф = BA

    Unit: Wb (Weber)
    Derived Unit(s): T m2 (Testla-metre squared)
    Further Derived Unit(s): kg A-1 s-2 x m-2 = kg A-1 m-2 s-2 (kilogram per Ampere-metre squared-second squared)

    (T = kg A-1 s-2)
  2. jcsd
  3. Apr 15, 2007 #2

    Meir Achuz

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    Q should be I*t. I'm sure you knew that.
  4. Apr 26, 2007 #3
    My bad ... but I can't edit my thread !
    Last edited: Apr 26, 2007
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