26 Jun, 2012
PRESENTATION: In a rigid solid rotating around a fixed axis, the linear speed of each point increases with its distance to the rotation axis, while the angular speed is the same for all of them.
- Jogging on a Carousel, Alpha E. Wilson, Phys. Teach. 49, 570 (2011)
- Wiimote Experiments: Circular Motion, Minjoon Kouh, Danielle Holz, Alae Kawam, and Mary Lamont Phys. Teach. 51, 146 (2013)
INTRODUCTION: The circular movement is based on an axis and a constant radius of rotation, so the trajectory is a circumference. In a circular movement, we can define two different speeds, angular and linear, related through the radius of rotation value. The different points placed along the radius distance from the axis have different linear speed but the same angular speed. This experience shows the relationship between both of them.
OBJECTIVE: To show that the LEDs in our setup in the outer part of the disk have higher linear speed.
MATERIALS: cardboard, paper, LEDs, cables, plastic tube, a 4,5 volt battery, glue.
SETUP: Cut a disk of cardboard, cover it with paper. Locate the center of the disk and pierce it with the plastic tube that will act as the rotating axis. Place 10 LEDs in a row along the disk radius, from the center to the edge, and connect them to the battery.
EXPLANATION: The linear speed and radius are proportional, so the LEDs placed close to the disk border have higher linear speed than those placed close to the disk center, although the angular speed of all of them is the same.
CONCEPTS: Linear and angular speed, circular movement, tangential acceleration, radius, radian.
- Tipler P.A. Física. Barcelona: Reverté, 2010.
- De Juana J.M., Física General, Pearson, 2009.
- Serway R.A y J.W.Jewett. Física, Thomson-Paraninfo, 2010.
STUDENTS 2012-2013: Alba González, Carolina Gil, Aday Rivera, Jesús M. Gómez
LINK pdf STUDENTS (in Spanish):