At a certain instant during the motion of a small‐angle pendulum
PHYSICS · Multi-part · A Level · Physics · Further mechanics and thermal physics · Further mechanics and thermal physics
Problem
At a certain instant during the motion of a small‐angle pendulum, the bob of mass 0.25kg is observed to be 5.0∘ away from the vertical. The string length is 0.80m and air resistance is negligible. Take g=9.8ms−2.
(1) Calculate the linear displacement x of the bob from the lowest point of its trajectory at that instant.
(2) Determine the magnitude of the tangential restoring force acting on the bob at that same instant.
(3) Briefly interpret the sign of the restoring force in the context of the bob’s motion, even though you reported only its magnitude in part (b).