See how the motion of the simple pendulum is not-so-simple after
Things are roughened up and friction is now added to the
approximate simple pendulum
Get to grips with the variables behind the motion of a simple pendulum
Think about a car which starts to move really fast. What happens? Try to use analogy for the lift.
If you place an obstable for the thread you will have two pendulums of different length. Thus, the resultant period is a combination of periods for different lengths.