Question

A bob of mass 0.1 kg hung from the ceiling of a room by a string 2 m long is set into oscillation. The speed of the bob at its mean position is 1 m s^–1. What is the trajectory of the bob if the string is cut when the bob is

1. At one of its extreme positions,
2. At its mean position.

Answer 1

1. At each extreme position, the bob has zero instantaneous velocity. If the string is cut when the bob is in one of these extreme positions, only gravity acts on the bob, causing it to fall directly downward.
2. When the bob is in its mean position, it is influenced by gravity. At this mean position, the bob moves with a velocity of 1 ms^-1 along the tangent to the arc, which is in the horizontal direction. If the string is cut at the mean position, the bob will behave as a horizontal projectile and will follow a parabolic path.