PURPOSE: To show that the centrifugal force of uniform circular motion (UCM) is a function of the radius, and to show that the directions of the radial and tangential vectors of UCM are constantly changing.
DESCRIPTION: A large circular aluminum platter is made to rotate at about 40 rpm by a motor control, shown in the above left photo. A puck is placed onto the rotating platter. At the center of rotation the puck experiences little force. When the puck is placed further out from the center it feels a greater force. Finally, when the puck is placed sufficiently far away from the center of the platter it experiences sufficient force to overcome the static friction and it will slide off the platter.
Vector arrows are placed onto the rotating platter and the speed is slowed to about 3 or 4 rpm, as shown in the above right photo. As the platter slowly rotates the tangential and radial vectors are observed to constantly change direction.
EQUIPMENT: Platter, motor, control, c clamp.
SETUP NOTES: Adjust the motor speed to 32 so the puck will slide when placed on the marked brown ring.