Here on Earth, friction is an unbalanced force that will cause moving objects to negatively accelerate. A top is a classically fun toy that spins for a period of time. Tops stop spinning because of friction forces between the top and the surface it is spinning on (as well as some friction with the air). Using a top that doesn't stop (available at Educational Innovations) and a normal top, this demo offers a discrepant event for students to experience. They know that all tops stop, but don't neccessarily know why, and they will be especially preplexed when they see a top that does not stop spinning. Watch the video to see it in action and to see why it doesn't stop spinning.
Entries in motion (11)
This is one of my favorite demos to show how mass determines the inertia of an object. If you are going to do this demo in class, make sure you use fishing line that can handle the highest tension possible (great demo for tension as well) that you can buy at a local sporting goods store. I used goop adhesive to attach a paper clip to the golf ball, so that I could tie the fishing line to the golf ball. I tied both objects to the metal beams of the drop down ceiling in my classroom. Watch the video to see how the demo works.
At the end of the year, students get a chance to be the scientists in several projects. One of my absolute favorites is the water bottle rocket. The video shows the general design of the rockets and several launches. What I love about the project is that they chose one variable to change that will increase flight distance. Variables include fin shape, fin size, fin placement, volume of water, etc. I also love that there is not just one design that works. Here is the handout that I give to students.
Motion is the change in position over time. Students often have a difficult time understanding that concept graphically, which is one of the big 8th grade science standards. Vernier's Go!Motion sensor and software are excellent demonstration tools. The video demonstrates how both of them work together. Usually when I introduce it, I just give a volunteer student a big (1 x 1 yard) whiteboard and tell the student to walk towards and away from the sensor. The students can see the graph on the large video screen. They quickly pick up that the farther away from the sensor the student is, the higher on the graph the line is and vice versa. I have them draw graphs what what they think certain types of motion are and then we see if we can replicate the graph. The software also allows a prediction graph to be drawn and then students can see if they can walk that same motion graph. In later lessons, acceleration graphs are explored. Having a class set would be ideal, but having one sensor with a computer hooked up to a video projector will work just fine.