Period is seconds/cycle. So just divide number of seconds by the cycles completed. Hope this helps!
Answer:

Explanation:
The amplitude of he combined wave is:

A, is the amplitude from the identical harmonic waves
B, is the amplitude of the resultant wave
θ, is the phase, between the waves
The amplitude of the combined wave must be 0.6A:

Lean your shoulders back and your waist forwards. Use your arms as a counter weight.
The energy added here is potential energy since it is moving upward 180 meters in a gravitational field. This is then turned into KE when it rolls down. 2524N x 180m = 454,320J