Explanation:
a) Frequency is cycles per second.
f = 8 cycles / 15 s
f = 0.533 Hz
b) Period is the inverse of frequency.
T = 1/f
T = 1.88 s
c) A pendulum is an example of simple harmonic motion.
d) There are 4 amplitudes in one full swing. So 8 full swings is 32 amplitudes. The distance per amplitude is:
A = 25 cm / 32
A = 0.781 cm