Frequency of string and tuning fork

[somecelxis]

Homework Statement

can someone teach me on this question? i really don't know how to start with it. the ans is 0.38m and 4.1N

Homework Equations

The Attempt at a Solution

the working is in the second photo

 

[haruspex]

There seems to be some text missing from the question. The second sentence is incomplete. It reads "When ... and ... ". The reader expects some statement of what happens under those conditions, such as "a beat frequency of <some number> Hz is heard", but the sentence abruptly ends.

 

[rude man]

I didn't see any discontinuity. Maybe the OP corrected the image?

EDIT: NM I see your point. The wording is horrible. The problem is not fully stated no matter how you rearrange the given data. The tuning fork frequency is obviously needed. The 3 Hz is a beat, not the tuning fork frequency. Etc.

 

[AlephZero]

There seems to be line missing from the question between

... a tuning fork of
?
frequency of 3 Hz ..

 

[somecelxis]

I didn't see any discontinuity. Maybe the OP corrected the image?

EDIT: NM I see your point. The wording is horrible. The problem is not fully stated no matter how you rearrange the given data. The tuning fork frequency is obviously needed. The 3 Hz is a beat, not the tuning fork frequency. Etc.

why The 3 Hz is a beat, not the tuning fork frequency?

 

[rude man]

why The 3 Hz is a beat, not the tuning fork frequency?

Well, for one thing you couldn't hear a 3 Hz tuning fork.
For another, the problem is horribly badly described so I made a guess that the 3 Hz is intended to be a beat frequency and the tuning fork frequency was omitted.

 

[somecelxis]

Well, for one thing you couldn't hear a 3 Hz tuning fork.
For another, the problem is horribly badly described so I made a guess that the 3 Hz is intended to be a beat frequency and the tuning fork frequency was omitted.

why I couldn't hear 3hz tuning fork?

 

[AlephZero]

why I couldn't hear 3hz tuning fork?

The lowest frequency that humans can hear is about 20Hz.

You can see something vibrating at 3Hz if the amplitude is big enough. But a "tuning fork" that vibrated at 3 Hz would be about 1m long, which is nonsense.

 

[rude man]

A healthy young human ear can hear sounds from 20 Hz to about 15,000 Hz. Most people's range is less than that.