Physics 141 Week 6
Circular Motion
Airplane on a String
A battery powered airplane provides enough thrust to maintain uniform circular motion which can be used to introduce the topic while discussing various defining attributes.
Arrows on a Wheel
Using the attached magnet the bike wheel can stick to your blackboard. Magnetic arrows can then be added in various directions to illustrate circular motion vector quantities.
Centripetal Force
Colored Water in a Bottle
Swing the bottle in a vertical circle and show how the water’s inertia causes it to appear to be pushed towards the end of bottle, or use this demo to show how an object's velocity or radial distance influences circular motion.
Measuring the Centripetal Force
Swing the ball around in a horizontal circle and have a student attempt to read the spring scale. This can also be used both qualitatively and quantitatively to show how varying velocity can affect the centripetal force.
Equilibrium and Circular Motion
This demonstration is a great qualitative way to show your students how the ratio between an object's tangential velocity and its radius of rotation can influence the centripetal force. Can you calculate what period is necessary to suspend the mass "X" cm below the tube?
Loop-the-Loop
Using a loop-the-loop you can discuss circular motion, energy conservation, and pose many engaging and intricate questions to your students. For example, what happens to the normal force at the top of the circle if the ball barely makes it around?
Centrifugal Force Puzzle
Pose this question to your students, "If the centrifugal force is in fact a pseudo-force, then why do these balls drift towards the edge when the device is rotated?" Use this puzzle to engage your students in a critical thinking exercise about inertia.
Centripetal Force Apparatus
Rotate the device to begin stretching the spring. Have your students calculate a centripetal force using it's radius and a calculated period. From here, use a spring scale to verify their theoretical predictions.
Ball on a String
Show that there must be a centripetal force (tension) to allow for circular motion, otherwise the rope would not remain taught. You can also swing it vertically to discuss what happens to the centripetal force at the top and bottom of the loop.
Water in a Bucket
Using a bucket full of water, you can engage students in a discussion about what is necessary to stay dry while swinging it over your head. You could even derive the minimum velocity (when normal force = 0N) necessary to keep the water in the bucket!