00:01
All right.
00:03
So for this problem, so we have a ball which is fencing up with initial velocity v0.
00:13
And we also have electric field, which is pointing up.
00:19
And we know that v0 initial velocity is 1 .92 meters per second.
00:26
And the magnitude of electric field is 3 .6 times 10 to the 4th.
00:32
Newton for cool, and the other condition is we know that the ball travel a distance of h equal 6 .98 centimeters in t equal 0 .2 seconds.
00:52
So the question is we want to find out, let me see, we want to find out the charge mass ratio q over m.
01:01
So to figure this out, we need to find out the velocity at a t equal to 0 .2 seconds.
01:12
So to do that, we can utilize the energy conservation law.
01:18
So the initial energy is the initial kinetic energy, plus the potential energy stored in the electric field, which is the eq.
01:28
Let's say this is just the h.
01:30
So this is the work done by the electric field and this is the initial initial kinetic energy energy and this will be equal to half m times v1 squared so v1 is the velocity at a at a time t equal to 0 .2 seconds okay plus the the work down by the gravity mg h so so we can solve for v1, we obtain v1 is plus or negative.
02:14
Let me see, it's v0 squared, minus 2 gh and plus 2eh q over m...