00:01
So in this problem, we're told that a photon is suspended in the air.
00:05
So, and we want to know what must be the electric force.
00:10
So we know that the force of gravity is down.
00:13
The electric force is up.
00:16
Whoops.
00:18
And so they must be equal and opposite.
00:20
So we know that f .e is equal to fg.
00:24
F .e is equal to q times the electric field, which is what we're solving for, i think, right? yeah, and then fg is equal to g, mass of earth, mass of proton divided by the radius of the earth squared.
00:44
And because that's the position of the center of mass, the earth.
00:47
And so then e is then this whole right side divided by q.
00:56
So i'll just kind of erase that.
00:59
So everything's right.
01:00
Okay, excellent.
01:01
And so now it's time to plug everything into a calculator.
01:05
So we are doing 6 .67 times 10 of minus 11, 598, 10 of the 24...