94c4lt1 Posted January 4, 2005 Report Share Posted January 4, 2005 Hi Guys, I am new and I was hoping I could get some help with an equation. time= (.15 w-s/mm^2)/(720 uW/cm^2) w-s is watt seconds and uW is microwatts. mm^2 is millimeters squared and cm^2 is centimeters squared. I have it simplified pretty well, only I am having difficulty with the w-s and w. I am not sure how to simplify that more. I can convert w-s to joules, but I can't get the energy to convert to power (watts). Can anyone help solve this and tell me how to do it? Thanks. Link to comment Share on other sites More sharing options...
Tormod Posted January 4, 2005 Report Share Posted January 4, 2005 Welcome! Hope Bo or Tim gets a chance to help you out here. They are our math experts. Link to comment Share on other sites More sharing options...
94c4lt1 Posted January 4, 2005 Author Report Share Posted January 4, 2005 Welcome! Hope Bo or Tim gets a chance to help you out here. They are our math experts. Thanks for the welcome. Great site you have here. Thanks. Link to comment Share on other sites More sharing options...
Tim_Lou Posted January 4, 2005 Report Share Posted January 4, 2005 well, you just have to convert the units to standard units and simplify it.(.15 w-s/mm^2)/(720 uW/cm^2)=(1.5*10^5 ws/m^2) / (7.2 w/m^2)time comes out as 2.1*10^ 4 seconds. Link to comment Share on other sites More sharing options...
IrishEyes Posted January 4, 2005 Report Share Posted January 4, 2005 Tim, you are just so cute sometimes! I have NO DOUBT that you will become famous in some way :) I mean, really... you make it sound so simple... "well, you just have to convert the units to standard units and simplify it." ... like it's something every single one of us does all day long, right? I have a hard time remembering to 'carry the one' sometimes, and you act as if this were no more than adding 2+2... amazing. Link to comment Share on other sites More sharing options...
Tormod Posted January 4, 2005 Report Share Posted January 4, 2005 No, in the other thread he couldn't comment on infamous' calculations (I mean, any kid could). So Tim's not a wizard, he's just faking it. :) Link to comment Share on other sites More sharing options...
94c4lt1 Posted January 4, 2005 Author Report Share Posted January 4, 2005 well, you just have to convert the units to standard units and simplify it.(.15 w-s/mm^2)/(720 uW/cm^2)=(1.5*10^5 ws/m^2) / (7.2 w/m^2)time comes out as 2.1*10^ 4 seconds. Thanks for you help. Doing it your way gives me 2.1*10^3 though.... Can someone double check this for me? When I simplify, I get: (150 w-s/m^2)/(.072w/m^2)=2083.3 Am I doing something wrong? Link to comment Share on other sites More sharing options...
94c4lt1 Posted January 4, 2005 Author Report Share Posted January 4, 2005 well, you just have to convert the units to standard units and simplify it.(.15 w-s/mm^2)/(720 uW/cm^2)=(1.5*10^5 ws/m^2) / (7.2 w/m^2)time comes out as 2.1*10^ 4 seconds. My other question is the units. w-s means watts per second = w/s. From the P=W/t (power equals energy divided by time). Here is the unit equation: ((w/s)/m^2)/(w/m^2) = (w/sm^2)/(w/m^2) = 1/s Or am I wrong somewhere? Link to comment Share on other sites More sharing options...
Tim_Lou Posted January 6, 2005 Report Share Posted January 6, 2005 ((w/s)/m^2)/(w/m^2) = (w/sm^2)/(w/m^2) = 1/syes, it is true, but it the ws means w/s in your equation:time= (.15 w-s/mm^2)/(720 uW/cm^2)it cannot be true, it would be:1/time= (.15 w-s/mm^2)/(720 uW/cm^2) anyway, yeah im not a math wizard, im just a science and math nerd. :) Link to comment Share on other sites More sharing options...
Tim_Lou Posted January 6, 2005 Report Share Posted January 6, 2005 time= (.15 w-s/mm^2)/(720 uW/cm^2)(.15ws/mm^2) * (10^6 mm^2/ 1 m^2) = 1.5*10^5 ws/m^2(720 uW/cm^2) * (1w/10^6 uW) * (10^4 cm^2 / 1 m^2) = 7.2 w/m^2 hmm, maybe you forgot the mm^2 and cm^2?1 m^2 = 1000*1000 mm^2 = 10^6 mm^21 m^2 = 100*100 cm^2 = 10^4 cm^2 Link to comment Share on other sites More sharing options...
Tormod Posted January 6, 2005 Report Share Posted January 6, 2005 "not a math wiz". Lol. :) Link to comment Share on other sites More sharing options...
maddog Posted January 8, 2005 Report Share Posted January 8, 2005 Hi Guys, I am new and I was hoping I could get some help with an equation. time= (.15 w-s/mm^2)/(720 uW/cm^2) w-s is watt seconds and uW is microwatts. mm^2 is millimeters squared and cm^2 is centimeters squared. I have it simplified pretty well, only I am having difficulty with the w-s and w. I am not sure how to simplify that more. I can convert w-s to joules, but I can't get the energy to convert to power (watts). Can anyone help solve this and tell me how to do it? Thanks. I will take a stab... time= (.15 w-s/mm^2)/(720 uW/cm^2) where uW = 10^6 W, cm = 10 mm, so time = (15 Ws/cm^2)/ 720 * 10^-6 W/cm^2= (1/48) * 10^6 (Ws/cm^2)/(W/cm^2)= (1/2)(1/4)(1/6) * 10^6 Sec= (.125)(.167)*10^6 sec~= 2*10^4 sec Yeah your big goof is mixing mm with cm, a common problem.There are 10 mm to a cm. The units you mention is in mks system (in meters) yetthe equation is to be put in one or the other {mm, cm, m -- take your pick} Hope this helps. I am a bit rusty, though I will stand by my work. Maddog Link to comment Share on other sites More sharing options...
ImZ Posted January 8, 2005 Report Share Posted January 8, 2005 I think you are doing this all wrong guys. But check my solutsion. Maybe I`m wrong because I have slept only 3 hours and I often make mistakes when I`m tired. I really hope I didn`t make mistakes this time. Check it. Link to comment Share on other sites More sharing options...
ImZ Posted January 8, 2005 Report Share Posted January 8, 2005 Here it is Link to comment Share on other sites More sharing options...
hashes Posted January 8, 2005 Report Share Posted January 8, 2005 time= (.15 w-s/mm^2)/(720 uW/cm^2)time= (.0015w-s/cm2)/(720uW/cm2)time=(.0015w-s/cm2)/.000720W/cm2)time=2.08333...3s Link to comment Share on other sites More sharing options...
94c4lt1 Posted January 10, 2005 Author Report Share Posted January 10, 2005 time= (.15 w-s/mm^2)/(720 uW/cm^2)time= (.0015w-s/cm2)/(720uW/cm2)time=(.0015w-s/cm2)/.000720W/cm2)time=2.08333...3s After redoing the equation and checking a few things, I think Tim was right. I got confused when converting cm^2 to mm^2. I was just using 1cm=10mm when it is cm^2 to mm^2. So 1cm^2=100mm^2. Therefore the answer is 20833.33 s. Thanks for all the help guys. Wow there sure are alot of answers. InfiniteNow 1 Link to comment Share on other sites More sharing options...
ImZ Posted January 10, 2005 Report Share Posted January 10, 2005 As you wish but.....If you convert cm to mm then.....0,15 w-s/mm2: 0,072 w/mm2=2,083 s It`s your own choice but if Tim was here I belive he would admit he`s mistake.I`m absolutely sure that this solution is the right one. This equation is really simple and I really don`t think I was wrong :) Link to comment Share on other sites More sharing options...
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