Answer:
68.8 Hz
137.6 Hz, 206.4 Hz
Explanation:
L = Length of tube = 2.5 m
v = Velocity of sound in air = 344 m/s
Distance between nodes is given by

Where n = 0, 1, 2, 3, ...
Making n+1 = n

where n = 1, 2, 3 .....
For fundamental frequency n = 1

Frequency is given by

The fundamental frequency is 68.8 Hz
First overtone

Second overtone

The overtones are 137.6 Hz, 206.4 Hz
Distance , d = a+b

The unit of d is in meter and t is in seconds.
So the unit of a a must be meter.
Now we have unit of b

is meter.
So unit of b*

= meter
Unit of b = meter/

So unit of a = m and unit of b = m/

.
External = R
Internal = r
Volume of hemisperical = 2/3 π(R³-r³)
V= 2/3 π(9.1³ - 8.4³)
V= 336.9 cm³
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Connection to Big Idea about energy: Gravity creates gravitational potential energy. Gravitational energy relies on the masses of two bodies and their distance.
Connection to Big Idea about the universe: Gravitational force is exerted by all objects with mass throughout the Universe. It is what keeps the Earth and the planets in orbit around the Sun, and our Solar System in orbit around the centre of the Milky Way. Gravity is one of the forces involved in the birth of stars, their evolution and finally their death.
Connection to Big Idea about Earth: The gravitational force is responsible for many physical properties of Earth and consequently it affects the existence and the properties of living creatures on it. For instance, the existence, the chemical composition and the structure of Earth’s atmosphere was determined by Earth’s gravitational force.