Please help!
A string 70.2 cm long has a mass per unit
length of 0.000135 kg/m.
To what tension should this string be
stretched if its fundamental frequency is to
be 20 Hz?
Answer in units of N

Question

Please help! 
A string 70.2 cm long has a mass per unit
length of 0.000135 kg/m.
To what tension should this string be
stretched if its fundamental frequency is to
be 20 Hz?
Answer in units of N

rajat97 · Answer

the formula for fundamental frequency when the string is fixed at both ends is vw/2l
where vw is the velocity of the wave and l is the length of the string
now,
we can write vw=(T/mu)^1/2
where T is the tension and mu is mass per unit length
so we can write 
$$f = (T/\mu)^1/2 \div l$$
insert mu=0.000135 and l=0.702 meters and f=20hz
so you get T=0.027N

rajat97 · Answer

i hope this helps you:)

anonymous · Answer

That is a different formula than the original one I had been using (and getting incorrect answers) but sadly the tension you got is still incorrect. But thank you @rajat97

rajat97 · Answer

yeah you're welcome but i'll try it once again

rajat97 · Answer

is it around 0.1025 N??

anonymous · Answer

That's incorrect also maybe its the values because somewhere I saw that the mass per unit length should be converted from kg/m to gm/m

rajat97 · Answer

i don't think so as we need to solve it in SI units to get the tension in newtons

anonymous · Answer

You're probably right, I'm not too good at figuring out equations O.o I really appreciate your help

rajat97 · Answer

it's my pleasure!

rajat97 · Answer

and the formula should be

rajat97 · Answer

$$f=\sqrt{T/\mu} \div 2l$$ for the fundamental frequency

rajat97 · Answer

do you have any diagram for this question ???

anonymous · Answer

sadly I do not but I had tried that equation before and I got a giant number for some reason..

rajat97 · Answer

do you know the answer for this question??

anonymous · Answer

Sadly I do not I only get 7 chances to get it and I've used 5 and I haven't gotten it

rajat97 · Answer

is it any website or something elese??
and my new answer is 0.10644N
so many answers to one question(lol)

anonymous · Answer

Omg that answer is correct! lol thank you for the help!

rajat97 · Answer

thanks for the medal
wow ! is it really correct??

anonymous · Answer

Haha yes it was correct and you're welcome for the medal

rajat97 · Answer

yeah!
and you deserve a medal for your patience!