I need math help

Discussion in 'General Chat' started by Marki, Apr 9, 2007.

  1. from my AP calculus class, just decided to tackle the over spring break hw and realized i never #$%#ing learned this shit

    1. Suppose that a cup of cocoa cooled from 90 degrees C to 60 degrees C after 10 minutes in a room whose temperature was 20 degrees. How much longer would it take the cocoa to cool to 35 degrees C?

    2. A radioactive substance decays at a rate proportional to the amount present. If one gram of a radioactive substance reduces .25 gram in four hours, find how long it will be until .1 gram remains.

    3. A pizza heated to a temperature of 350 degrees Fahrenheit, is taken out of an oven and placed in a 75 degree F room at time t=0 minutes. The temperature of the pizza is changing at a rate of -110e^.4t degrees Fahrenheit per minute. To the nearest degree, what is the temperature of the pizza at time t=5 minutes?
  2. Graphing calculator, plot regressions...
  3. 1 and 3 are newtons law of cooling problems. 2 is a halflife problem and they are the easiest type of differential equation. Look those terms up, there should be two equations with the variables defined somewhere in your textbook.
  4. Ae=Ao*.5 t/t(1/2) for the half life equation.
  5. t1/2 is 2hours
    Ae is .1 grams
    Ao is 1 gram
    t needs to be solved

    manipulate the equation:
    so t=((logAe/logAo)/log.5)*t1/2
  6. Man, thats horribly wrong.

    first you solve this for r:

    .25 = 1*e^(r*(4*3600))

    Then you solve this for t

    .1 = 1*e^(r*t)
  7. You're right. I looked up the wrong equation from my textbook.
  8. #$%# you, ive raped people for far less than this. you think you can #$%#ing come on SC.NET and just act like a #$%#ing hardass and order people around? Bad news for you, #$%#face, but tonights the night your luck runs out. You #$%#ing tell ANYBODY on these forums what to do again, and you're going to find out the hard way what a #$%#ing baseball bat to the side of the skull feels like. Think I'm #$%#ing kidding? I have your IP, I know who you are, and Im more than willing to settle this argument face to #$%#ing face. You call yourself "Hooligan"? We'll see who's the hooligan when one of us is lying face down in a pile of their own blood, shit, and piss. Try and order someone else on here around, and see what #$%#ing happens to you. I'm normally a calm guy but when I need to, I'm willing to break some #$%#ing face to get my point across, just #$%#ing test me you worthless sack of excrement.
  9. LAWLZ!!

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