00:01
Okay, i set up this problem with this charge, 5 .3 microculems at the origin, and then this charge, negative 4 microcolomes, is 1 .9 meters away.
00:15
So this blue distance is 1 .9.
00:17
I'm going to call the distance from the origin x, and i'm going to call this distance 1 .9 minus x.
00:25
So if we want to find the electric field equal to zero, electric field, the formula i'm going to use here is kq over r squared.
00:36
So first of all, let's do the electric field felt here from this charge.
00:43
Okay, it is k times 5 .3 microcoules over x squared.
00:55
Next, let's do the same thing with the green distance, and we're going to have to set them equal to each other.
01:06
One is positive, one is negative, so they'll act against each other and cancel each other out.
01:12
So the green one is going to be k, q, times, it doesn't really matter that it's a negative four.
01:21
I mean, it does because the directions are canceling out, but in our calculations, here, this is what we need.
01:31
I'm going to set those equal to each other and this radius here is squared.
01:37
Notice that the k's cancel out.
01:41
Notice that i wrote a cue here and i didn't mean to because i actually knew the charge that i wrote in.
01:47
Now let's take the square root of both sides.
01:50
That's the easiest next step...