 Now we can look at the second problem on the back side of your worksheet for today's virtual lecture and Again, I've taken the problem and just kind of enlarge the text a little bit. So it's easier to read in the video a Small charge particle has a mass of two point four zero e to the minus fifth kilograms and a charge of 4.50 e to the minus ninth Coulomb if this particle travels at a speed of five point five zero meters per second perpendicularly Into a 50 Tesla magnetic field. What is the radius of the resulting path? Show your work So the first thing I want to say here is what I'm basically describing is a particular device that was described in one of the videos called a mass Spectrometer So you want to go back and you want to watch the videos related to a mass spectrometer And this is the part of the device which actually comes right after the velocity selector So you notice I use the same values that we had in the previous problem So the five point five meters per second is the speed coming out of the velocity selector And it continues in a region of magnetic field, but the electric field isn't there anymore So now we can talk about the values we have So we'll start off with the mass and the charge and 2.40 kilograms Hmm hold on that should be 2.40 e to the minus fifth kilograms a really small particle and it has a really small Charge as well. So this is a nano Coulomb Which makes a lot more sense because mass spectrometers don't work on large objects So rather than rerecord the video, I'll just use that as an extra teaching moment there and then again, we've got values that came out from the Velocity selector and so I know my speed in my magnetic field So those are the knowns for this particular path problem Now right now it would seem like I don't quite have enough information But if you go back and you watch the pre lecture video about the mass spectrometer or look in your textbook We see that there's an equation which relates The Centripetal force to the magnetic force and as we go through that if we solve that for The radius I can see how it's related to these other quantities Now it depends on the mass and the velocity it also depends on the charge in the magnetic field Now you can tell from some of my copying and pasting here that I actually have this already plugged in and So I could plug these known values into this equation And I'm going to let you do that remember whenever you have two things in the bottom You want to use an extra set of parentheses around there now real quick talking about these units if You go back and you replace Tesla with what we had from the earlier videos and Then you replace Newton with what a Newton is equal to you'll see how this all cancels out But I also want to remind you what is it? We're solving for We're looking for a radius What kind of unit should I get for a radius? So again on your problem here You want to make sure that you show all your work and I haven't shown everything here You have to do the last step of actually solving the problem and putting down the final units If you're not quite understanding go back Watch the video on the mass spectrometers. You understand what we're trying to do and where these equations come from So that we're able to actually solve this problem