Ahh, thanks.. I have a problem where I can't concentrate and I'm usually thinking about 3 things at once when I'm doing a problem, so I usually overcomplicate things :-p
Thanks for the help on this problem. Does anyone know a good trick to concentrate? I notice that if I drink coffee I can...
Here's the question:
What are the strength and direction of an electric field that will balance the weight of a 1.0g plastic sphere that has been charged to -3.0nC?
Ok, here's what I did.
Knowns
q = -3nC
m = 1.0g
weight force = 9.8 gm/s^2 (I assume this is done on surface of earth)...
Ok, for some reason, I'm getting the wrong answer. It's asking for how many electrons were removed from an object that has gained a +5nC charge. Here's my setup.
(1.60x10^(-19)) / ( 5*10^(-9))
I'm getting 3.2*10^(-11)
yet book says the answer is actually 3.13*10^(-10)
wtf?
... *sigh* I was so used to seeing a 0 and just subtracting by 0 that I forgot cos(0) is in fact NOT 0... Is it bad that I take shortcuts without even realizing I'm taking them? :cry:
EDIT: I meant WRONG shortcuts =)
Ok, so we have
\int_{0}^{1}\left(\sin{2x}*\cos{2x}\right)dx
Using the double angle forumla we change the integrand
(1/2)\int_{0}^{1}\left(2*\sin{2x}*\cos{2x}\right)dx
which converts to
(1/2)\int_{0}^{1}\left(\sin{4x}\right)dx
This is where I run into trouble... I'm trying to...
Ahh, I see what I did I think. I think I tried to just throw out the 1 and ended up with (8^(3/2))/3
Thanks for the help!
It's hard to stop from taking shortcuts! Argh! :redface:
Ok, I've been doing work for about 4 hours straight and I think my brain is fried. I know this is easy, it is just not working in my head.
Anyway, the problem is this:
Integrate the sqrt(4x) + sqrt(4x) on the interval 0 to 1
I get, (8^3/2)/3 + (8^3/2)/3 but apparently this is not right...
Ok, I've been doing work for about 4 hours straight and I think my brain is fried. I know this is easy, it is just not working in my head.
Anyway, the problem is this:
Integrate the sqrt(4x) + sqrt(4x) on the interval 0 to 1
I get, (8^3/2)/3 + (8^3/2)/3 but apparently this is not...