00:01
In this question, we have a magnetic field that is pointing to the north.
00:06
And in the diagram here, the north is the right and there's a proton that's moving through through this magnetic field vertically downward.
00:17
So this is the proton here.
00:19
It has charge of q.
00:21
Which is the elementary charge 1.6 and sent to the power -19.
00:25
And it's pointing and smoothing downward.
00:28
No, we're interested in finding that magnetic force.
00:32
So f.
00:33
B.
00:33
From the definition of it equal to q.
00:36
V.
00:37
Cross b, which is equal to q.
00:43
We'll see b.
00:46
B b.
00:47
Sine theta.
00:50
Now from the diagram, it is clear that data equals 90 degrees but we don't have the velocity.
00:58
So the velocity here is missing.
01:02
That's what we're going to try to find.
01:03
Now, we're going to use the definition of the kinetic energy which is equal to have m.
01:12
V.
01:12
Square.
01:14
And from this definition we can write v equals to two times the kinetic energy divided by the mass under the square root...