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I need a unit Conversion

  1. Jul 9, 2015 #1
    Hi ALL
    i need to unit Conversion :
    from: 28.8 Volts/(Meter/Second) to (.............) Volts/(Inch/Second)
    from: 28.8 Volts/(Meter/Second) to (.............) milliVolts/(milliMeter/Second)
    Thanks
     
  2. jcsd
  3. Jul 9, 2015 #2

    Mentallic

    User Avatar
    Homework Helper

    Hi and welcome to PF!

    Let
    Volts = V
    Meter = m
    Second = s
    Inch = in

    then
    [tex]\frac{V}{m/s}=\frac{Vs}{m}[/tex]
    while
    [tex]\frac{V}{in/s}=\frac{Vs}{in}[/tex]

    So if you were given a problem that said, for example, the metal costs $10/m, then could you figure out how much it costs per inch instead? That is, what is the value of x such that

    [tex]\frac{$10}{m}=\frac{$x}{in}[/tex]

    If you can figure this out, then your problem is essentially the same because we can ignore the Volt-seconds in the numerators since they're both equivalent (think of them as merging into the $ symbol in my example).
     
  4. Jul 10, 2015 #3
    I do not understand your answer
    Do you can , give me more Explain

    Are you mean , like this:
    (v.s/m)=(v.s/in)
    (28.8v*1s/1m)=(xV*1s/39.4in)
    then
    28.8 v(m/s) = 1135 v(in/s) ?????

    ++++++++++++++++++++++++
    your example:$10/m to x$/in
    i thenk
    1m=39.4in
    $10/39.4in = $0.254/in
     
  5. Jul 10, 2015 #4
    Thanks, now I understand (Excellent)

    1 m/s = 39.4 in/s
    28.8v/(m/s) / 39.4v/(in/s) = 0.73 v/(in/s)
    then
    28.8v/(m/s) = 0.73 v/(in/s)
    it's good
    but,What about the second question
    from: 28.8v/(m/s) to (.........)mv/(mm/s) ???
     
  6. Jul 10, 2015 #5

    Mentallic

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    Homework Helper

    You can make it more simple for yourself by ignoring a lot of the common units.
    [tex]28\frac{V}{m/s}=x\frac{V}{in/s}[/tex]
    We know that 1m = 39.4in, therefore we convert metres to inches by making that substitution wherever we see metres.
    [tex]28\frac{V}{39.4in/s}=x\frac{V}{in/s}[/tex]
    And cancel all of the common units on both sides (which is the same as dividing both sides by [itex]V/(in/s)[/itex]) to get
    [tex]\frac{28}{39.4}=x[/tex]

    Now for the next question, again, do the substitutions as I've just shown you. 1000 millivolts = 1 volt, 1000mm = 1m.

    Note: remember we are striving for simplicity, so in your first problem, you could have cancelled common factors by going straight from

    [tex]28\frac{V}{m/s}=x\frac{V}{in/s}[/tex]
    to
    [tex]28\frac{1}{m}=x\frac{1}{in}[/tex]
    by cancelling V/s. This helps to draw focus onto the problem at hand and not get messed up with all of the units.
     
  7. Jul 10, 2015 #6
    http://im86.gulfup.com/ckruO5.png [Broken]
     
    Last edited by a moderator: May 7, 2017
  8. Jul 10, 2015 #7

    Mentallic

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    Homework Helper

    Very good, but you don't need to do it in 2 steps. Do it all in 1.

    [tex]28.8\frac{v}{m/s}=x\frac{mv}{mm/s}[/tex]
    Converting the LHS (left hand side):
    [tex]=28.8\frac{1000mv}{1000mm/s}[/tex]
    Cancelling the 1000's
    [tex]=28.8\frac{mv}{mm/s}[/tex]

    Hence x=28.8
     
  9. Jul 10, 2015 #8
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