Represent and reason.
You have a small bob on a long string (a pendulum). The pendulum bob swings back and forth, as shown in the figure. At each of the marked points in the figure, the coordinate system consists of an axis in the radial direction (r axis) and a perpendicular axis in the tangential direction (t axis). Disregard air resistance. Complete the tables that follow for positions shown in the figure. Points I and V are the highest points of the swing.
(a) Accelerations: Estimate the direction of the bob's acceleration at each of the points. III IV , / When the bob is moving down: moving right. moving up:
When the bob is moving up:
When the bob is moving left:
When the bob is moving down.
(b) Force Diagrams: Draw force diagrams for the bob at the 5 points. Make sure the arrow length(s) is/are proportional to the magnitude(s) of the force(s). Use a polar coordinate system. II IIT IV V When the bob is moving down: moving right: moving up:
When the bob is moving up:
When the bob is moving left:
When the bob is moving down: