I have exams in convertions...need serious help

Questions and answers on how to convert things from one unit or system to another

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I have exams in convertions...need serious help

Postby Ammar » Sun May 13, 2007 10:27 pm

Please help me to convert such hard methods, I'm a medical students in Slovakia and I have silly subject called biophysics and I have exam about many convertions please help me because I really fed up searching on the net like idot.
Here you are what I really need to convert:
Express in given units
1422 g = hg
71 ct = cm
3.25 hPa = kPa
0°C = K
5379 A.s = C
39 pF = nF
16 mW = J.s-1
13 GN.m = kJ
0.96 kN = mN
7 W.s + 65 cW.s = J
150 s = min
318 Bq = s-1
9.456 Hz = mHz
821 µA = aA
84 kV + 35V = MV
24.65 MΩ = TΩ

Please I'm looking for urgent help today and show me how does it work?? thanks
Ammar
 

Postby Guest » Sun May 13, 2007 11:37 pm

I can't help with this one. I don't know what ct is the symbol for (some local unit?) but it is nothing I can convert to centimeters.
71 ct = cm
I have grouped the others by underlying principle.

These are all examples of SI prefixes, which are merely other ways of expressing powers of ten.
Hecto- is the prefix for 100, so 1422 g = 14.22 x 100 g = 14.22 hg. You have to learn to recognize all the prefixes as their power of ten.
1422 g = hg
3.25 hPa = kPa
39 pF = nF
0.96 kN = mN
9.456 Hz = mHz
821 µA = aA
0.96 kN = mN
24.65 MΩ = TΩ
On this last one, you have to express both terms in the same unit before you can add.
84 kV + 35V = MV

The SI has a few odd conversions that are not powers of ten. Kelvin is the unit of absolute temperature and 0°C = 273.15 K. There are 60 s in 1 minute, so 150 s = 2.5 min. All you can do is memorize them, but rejoice there aren't as many odd factors as in the Imperial/Customary system still somewhat used in the UK and US.

The SI has several "derived" units which are an extension of physical principals. C is coulomb, the unit of charge, and and a charge flow 1 C/s is by definition a current of 1 A. Similarly, power is the rate of flow of energy and 1 J/s = 1 W, and energy is force times distance over which it acts. If your school has not taught you these concepts, I recommend downloading the SI Brochure from the BIPM in France (text is available in English and French.) to understand the SI system of measurement.
5379 A.s = C
16 mW = J.s-1
13 GN.m = kJ
7 W.s + 65 cW.s = J
318 Bq = s-1
Guest
 

Thanks too much but.......

Postby ammar » Sun May 13, 2007 11:46 pm

Thanks too much for helping me and for your advice and as you know I'm going to be a doctor or dentist I won't need all of these things in my job.

By the way I understood what you wrote about the first part but what about the second part? are the value the same no changing???
I mean the following
5379 A.s = C
16 mW = J.s-1
13 GN.m = kJ
7 W.s + 65 cW.s = J
318 Bq = s-1

waiting your reply
ammar
 

Sorry but can you ....

Postby Ammar » Sun May 13, 2007 11:48 pm

Sorrrrrrrrrrry but can you help me by writing the answer please please
Ammar
 

Re: Thanks too much but.......

Postby Guest » Sun May 13, 2007 11:52 pm

ammar wrote:Thanks too much for helping me and for your advice and as you know I'm going to be a doctor or dentist I won't need all of these things in my job.

By the way I understood what you wrote about the first part but what about the second part? are the value the same no changing???
I mean the following
5379 A.s = C
16 mW = J.s-1
13 GN.m = kJ
7 W.s + 65 cW.s = J
318 Bq = s-1

No, they all have meaning. You have to understand the relationship between units. An ampere*second is the same thing as a coulomb, a watt is the same as a joule*second, but they have also added a prefix you will need to convert. A newton*meter is the same a joule (but note the prefix). The becquerel is a unit of radiation activity, you may need to understand it as a doctor. It is the number of particle emissions per second from a radioactive mass.

If you have not been taught these concepts, I strongly recommend the SI brochure to understand the concepts rather than viewing it as "conversion" problems.

waiting your reply
Guest
 

Postby Guest » Sun May 13, 2007 11:55 pm

Sorry. I typed my response in the middle of what I quoted from you. I hope you can follow it as I can't edit it.
Guest
 

Re: Thanks too much but.......

Postby Guest » Mon May 14, 2007 12:00 am

ammar wrote:5379 A.s = C
16 mW = J.s-1
13 GN.m = kJ
7 W.s + 65 cW.s = J
318 Bq = s-1


1 A.s = 1 C, so answer is 5379 C

1 W = 1 J/s, but note the milli- prefix, so
16 mW = 16 mJ.s-1 = 0.016 J.s-1. I'll leave the others as practice for you. In the addition, remember both terms must have the same units before you can add.
Guest
 

Thanks and ..........

Postby Ammar » Mon May 14, 2007 12:22 am

Thanks my dear and really really you helped me a lot and you made me feel happy.

I really respect and i appreciate your knowledge and thanks isn't enough.

Take care and I hope I'm going to pass my exam tomorrow.....


My Regards.
Ammar
 


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