Answer
(a) A = 20 cm
(b) f = 0.25 Hz
Work Step by Step
(a) The motion moves between -20 cm and 20 cm. Therefore, the amplitude is 20 cm.
(b) From the graph, we can see that two cycles are completed in 8 seconds. Therefore, the period $T = 4~s$. This means that the frequency is:
$f = \frac{1}{T} = \frac{1}{4~s} = 0.25~Hz$
