If a yo-yo is spinning so that it makes 240 revolutions every minute, what is its period?

0.25 seconds.

Explanation:

The yo-yo does 240 revolutions in one minute, and we know that one minute has 60 seconds, then the revolutions per second can be calculated as:

240 rev/60s = 4 rev/s, this will be the frequency of the yo-yo

The frequency is actually written as: f = 4 Hz = 4 s^-1

We want to find the period of this yo-yo.

The period is the duration of one cycle, and we have the relation:

f = 1/T

Where f is the frequency and T is the period, then:

T = 1/f

And we know the value of f, it is f = 4 s^-1

Then the period will be:

T = 1/(4 s^-1) = (1/4) s

Then the period of the yo-yo is 1/4 seconds = 0.25 seconds.