What is meant by the natural frequency of vibrations of a body? Name one factor on which it depends?

State one condition for a body to execute the natural vibrations.

What adjustments would you make for tuning a stringed instrument for it to emit a note of a desired frequency?

A blade, fixed at one end, is made to vibrate by pressing its other end and then releasing it. State one way in which the frequency of vibrations of the blade can be lowered.