The answer is b. The crest.
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b. 460.8 m/s
Explanation:
The relationship between the speed of the wave along the string, the length of the string and the frequency of the note is

where v is the speed of the wave, L is the length of the string and f is the frequency. Re-arranging the equation and substituting the data of the problem (L=0.90 m and f=256 Hz), we can find v:

c. 18,000 m
Explanation:
The relationship between speed of the wave, distance travelled and time taken is

where
v = 6,000 m/s is the speed of the wave
d = ? is the distance travelled
t = 3 s is the time taken
Re-arranging the formula and substituting the numbers into it, we find:

Explanation:
the morning of the birthday party balloon filled with the 2.5 Litre of helium
temperature is 294kelvin
the party starts at the 4 p.m.
temperature rises 305 Kelvin.
the new volume = 4 litre.
At same temperature,
P
1
V
2
=P
2
V
2
(Boyle's law)
P
1
=10atm;P
2
=1atm
V
1
=4l=V
2
=8l
But while filling balloons from cylinder when pressure in cylinder becomes 1 atm then further filling is not possible (P
1
′
=9atm)
Let n be the number of balloons that can be filled.
∴P
1
′
V
1
=n(P
1
V
1
)
9×8=n(4×1)
n=
4
9×8
=18balloons