Demos: 1D-04 Radial Acceleration & Tangential Velocity
Balls with strings attached are in turn affixed to a disk that is spun rapidly by a motor. The strings stretch out radially, indicating a radial force. At any instant, the velocity vector of the ball is directed along the tangent. This is confirmed by having a razor blade cut the string as it comes to the vertical position. At this instant the ball’s velocity is horizontal so it acts like a horizontally launched projectile and lands in the catch box.
Directions: Test the strings for secure attachments, then turn on the motor. Once the motor has reached its steady speed, depress the switch that activates the razor blade. The balls will land in the box, one after the other, with a quick succession of “pops.”
Suggestions for Presentation: Begin by asking what direction mud slings off a rotating tire. Many students are not aware that the objects move off in the direction they are moving at that instant.
Applications: Think about a slingshot. At what point would you let the projectile go if you want to hit the target?