Apendulum with a mass of 0.100 kg was released. the string made a
7.0° angle with the vertical. the bob of the pendulum returns to its lowest point
every 0.10 s.
what is its period? what is its frequency?

The bob passes the lowest point twice during every complete swing.

The period of this pendulum is 0.2 seconds.

Frequency = 1/period

Frequency = 1/0.2 sec

Frequency = 5 Hz.  (A very very very short, fast pendulum.)

Note:  

The mass of the bob, the angle from the vertical (as long as it's small), the color of the string, and the day of the week have no effect on the period.  Only the length of the string has.

an ion is a charged atom or molecule. it is charged because the number of electrons do not equal the number of protons in the atom or molecule. an atom can acquire a positive charge or a negative charge depending on whether the number of electrons in an atom is greater or less then the number of protons in the atom.

gravity

explanation: