WEBVTT 00:00:03.920 --> 00:00:08.680 - Vernier's had a Dynamics Cart and Track System for some time. In our revised 00:00:08.680 --> 00:00:12.970 version we've taken all we've learned in using those carts and tracks with students 00:00:12.970 --> 00:00:17.650 to create a system that's ideal for teaching Dynamics and Kinematics in the 00:00:17.650 --> 00:00:21.820 Introductory Physics classroom. Let me walk you through some of the features of 00:00:21.820 --> 00:00:30.190 our carts and track. The carts have extremely low friction bearings. There is 00:00:30.190 --> 00:00:34.950 an anti-roll peg that keeps the cart from rolling off the lab table when it's simply 00:00:34.950 --> 00:00:41.410 placed there. Once you put it in the track and it's free to roll. The ends of the 00:00:41.410 --> 00:00:48.520 cart have easily removable tabs where you can keep magnets or hook and pile tabs for 00:00:48.520 --> 00:00:55.730 doing different kinds of collisions. The top surface of the cart is well labeled 00:00:55.730 --> 00:01:00.300 so that the student can attach sensors such as the dual-range force sensor, the 00:01:00.300 --> 00:01:06.220 low-g accelerometer, or the wireless dynamics sensor system. For example I can 00:01:06.220 --> 00:01:12.700 take a dual-range force sensor, just place it on the top surface, and the supplied 00:01:12.700 --> 00:01:19.940 bolt can be driven in, and now I've attached the force sensor to the top of my 00:01:19.940 --> 00:01:25.240 cart, and it's securely in place an d won't shift during the course of an 00:01:25.240 --> 00:01:34.090 experiment. The top surface of the cart also includes four mass trays. I can take 00:01:34.090 --> 00:01:40.930 a mass, put the mass in the mass tray and change the total mass of the cart without 00:01:40.930 --> 00:01:45.080 having to remove my dual-range force sensor. This way a student can do 00:01:45.080 --> 00:01:52.550 experiments looking at how the mass of the cart affects the dynamics and kinematics. 00:01:52.550 --> 00:02:02.090 Want to remove these and then show you the features of the plunger cart. 00:02:02.090 --> 00:02:07.090 Now the plunger cart is a different color. We did this intentionally so that in 00:02:07.090 --> 00:02:12.280 discussing collisions, students and teachers will no longer have to say, "this 00:02:12.280 --> 00:02:16.590 cart and that cart" or "my left and your right." We can simply talk about the grey 00:02:16.590 --> 00:02:22.620 cart or the green cart. The plunger cart is set-up so that you can do a variety of 00:02:22.620 --> 00:02:27.420 collisions. One interesting feature is that it's able to do super elastic 00:02:27.420 --> 00:02:33.600 collisions where the plunger extends on contact to the two carts. So I can set-up 00:02:33.600 --> 00:02:38.780 for a collision between the two carts and have the spring add energy to the system. 00:02:38.780 --> 00:02:44.940 I'll let the two drift together slowly and the plunger extends suddenly. It adds 00:02:44.940 --> 00:02:49.430 energy to the system. It doesn't change the momentum conservation. There are other 00:02:49.430 --> 00:02:56.410 pieces that come with the Dynamics Cart and Track System. For example many times 00:02:56.410 --> 00:03:01.050 Physics Instructors want to use a pulley with a photogate attached to the end of 00:03:01.050 --> 00:03:07.120 the track, the Dynamics Cart and Track System comes with a bracket and a pulley 00:03:07.120 --> 00:03:13.110 so that you can add your photogate and do experiments such as a Half-Atwoods 00:03:13.110 --> 00:03:19.060 Machine. The system is available for use both with motion detector, the standard 00:03:19.060 --> 00:03:23.810 ultrasonic motion detector or Vernier's unique and innovative motion encoder 00:03:23.810 --> 00:03:29.180 system. The motion encoder system has a cart that includes a sensor on the 00:03:29.180 --> 00:03:35.290 underside of the cart. That sensor sees the bars that are printed on the top 00:03:35.290 --> 00:03:39.980 surface of the track passed by and that information is sent back by an 00:03:39.980 --> 00:03:46.700 infrared beam to a receiver at the end of the track. This allows the system to 00:03:46.700 --> 00:03:52.300 record the motion of the cart as a function of time very cleanly with no 00:03:52.300 --> 00:03:58.610 problems from stray reflections from other equipment in the laboratory. Let's do a 00:03:58.610 --> 00:04:04.220 quick experiment showing how a cart on a ramp will work with a motion encoder 00:04:04.220 --> 00:04:07.210 system. I'm going to convert this track to a ramp 00:04:07.210 --> 00:04:15.080 by removing this foot. Now let's do a quick experiment studying the motion of 00:04:15.080 --> 00:04:20.370 the cart as it rolls up and down the ramp. So I'll start data collection in Logger 00:04:20.370 --> 00:04:27.700 Pro, give the cart a push, and allow the cart to roll back down and stop it. You 00:04:27.700 --> 00:04:34.050 see, very clean data, the position versus time graph shows only the motion of the 00:04:34.050 --> 00:04:38.490 cart. There are no extraneous spikes from other things going on in the classroom. 00:04:38.490 --> 00:04:43.560 The velocity versus time graph has a nice linear segment while the cart is freely 00:04:43.560 --> 00:04:48.460 rolling and the acceleration graph is usable as well showing constant 00:04:48.460 --> 00:04:54.880 acceleration as the cart was freely rolling on the ramp. And one thing that 00:04:54.880 --> 00:04:59.280 you almost never do in the Physics classroom when you use motion detectors is 00:04:59.280 --> 00:05:03.270 talk about the derivative of the acceleration. This is a quantity that's 00:05:03.270 --> 00:05:08.560 known as jerk and with the motion detector, you rarely get useful data. I 00:05:08.560 --> 00:05:15.660 can change my acceleration graph to a graph of jerk, and let me re-scale that, 00:05:15.660 --> 00:05:21.700 and you see that even the third derivative of the position as a function of time is a 00:05:21.700 --> 00:05:26.150 useful quantity when collected with a Vernier motion encoder system. The Vernier 00:05:26.150 --> 00:05:31.580 Dynamics Cart and Track System is actually an entire ecosystem of Physics education 00:05:31.580 --> 00:05:37.590 material. We have additional components that can be used with the carts to study 00:05:37.590 --> 00:05:46.580 other phenomenon. For example, I can pull my magnet tabs off of my cart and insert a 00:05:46.580 --> 00:05:53.210 friction pad. That friction pad has a piece that roll the rest on the track. And 00:05:53.210 --> 00:05:59.450 now I've got a cart moving with additional friction and I can study that phenomenon. 00:05:59.450 --> 00:06:05.040 We have other pieces available such as the bumper and launcher kit for doing momentum 00:06:05.040 --> 00:06:11.120 impulse experiments. We also have a variety of optics components that attach 00:06:11.120 --> 00:06:16.970 to the top of the track. We have thin lenses, we have mirrors, and we have 00:06:16.970 --> 00:06:22.600 diffraction apparatus in addition to a color mixing system. So the Vernier 00:06:22.600 --> 00:06:28.160 Dynamics Cart and Track System gives the Physics teacher a whole array of equipment 00:06:28.160 --> 00:06:34.000 with which to teach first year Physics.