The period of the wave is the reciprocal of its frequency.
1 / (5 per second) = 0.2 second .
The wavelength is irrelevant to the period. But since you
gave it to us, we can also calculate the speed of the wave.
Wave speed = (frequency) x (wavelength)
= (5 per second) x (1cm) = 5 cm per second
If you are designing a roller coaster that goes upside down, you may consider of course seat belts or something that goes around you to keep yourself safe.