Suppose you pluck a string on a guitar and it produces the note A at a frequency of 440 Hz . Now you press your finger down on the string against one of the frets, making this point the new end of the string. The newly shortened string has 4/5 the length of the full string. When you pluck the string, its frequency will be:
A. 350 Hz
B. 440 Hz
C. 490 Hz
D. 550 Hz

The newly frequency is 550 Hz.

(D) is correct option.

Explanation:

Given that,

Frequency = 440 Hz

Newly length

If the length of the string is L

We need to calculate the frequency

Using formula of frequency

....(I)

We need to calculate the newly frequency

Using formula of frequency

....(II)

Divided equation (II) and (I)

Put the value into the formula

Hence, The newly frequency is 550 Hz.

does anyone know or what?

conservation of mass

mass before something happens = mass afterwards