26).
The complete pattern of a pendulum is ...
-- out to one side
-- back to the center
-- out to the OTHER side
-- back to the center.
So, on the graph, the complete period is one up-loop and one down-loop.
That's 6 seconds. (b)
27).
This question is just asking for the frequency, without using the word.
Frequency is always (1/period). That's 1/6 of a second. (a)
(This kinda makes sense. If you want to do something in 6 seconds, you need to do 1/6 of it every second. Right ?)
