A mass is attached to the end of a spring...

Question

A mass is attached to the end of a spring. It is pulled down by a few cm and released. Within the next 0.4 seconds it passes through its rest position 4 times. what is the period of the oscillation?

Answer 1

If it passed through the rest position 4 times, it completed two cycles.

So, if it took 0.4 seconds to do 2 cycles, the period is 0.4 s / 2 cycles = 0.2 seconds / cycle (the period).