Answer:
The value is
Explanation:
From the question we are told that
The length of the string is
The mass is 
The frequency produced at fourth harmonic vibration(i.e n =4 ) is 
Generally the wavelength of the string is mathematically represented as

=>
=>
hmmmmmmmmmmmmmmmmm ask someone else sorry if im not helping
2 should be placed in the blank to make the equation balance. Btw, that's chemistry and not physics. Get it right.
Answer:
Here
Length (l) = 6 m
height (h) = 3 m
Load(L) = 500 N
Effort (E) = ?
we know the principal that
E * l = L * h
6 E = 500 * 3
6E = 1500
E = 250
therefore 250 N work is done on the barrel.