Final answer:
The correct answer is C) 180 degrees.
Step-by-step explanation:
In order to determine at what angle θ the rod will momentarily stop in its upward swing, we need to consider the motion of the rod as it swings back and forth. This type of motion is an example of simple harmonic motion (SHM), where the acceleration of the rod is directly proportional to its displacement from the equilibrium position and directed towards the equilibrium position.
At the maximum displacement, the acceleration is zero momentarily, resulting in the rod momentarily stopping. The angle at which this happens depends on the length of the rod and the acceleration due to gravity.
The equilibrium position of the rod is at the vertical position (180 degrees). As the rod swings upward, the displacement increases and reaches the maximum at 180 degrees. At that point, the acceleration is zero, and the rod momentarily stops in its upward swing.