Answer:
Pi(3.14) radians or 180º degrees
Explanation:
First of all, we need to obtain the wavelength of a wave traveling to the speed of sound and 420 Hz of frequency.
The formula is:

where l = wavelength in meters
With current values:
l = 336 [m/s]/420[1/s] = 0.8 meters
Since a complete cycle (360º or 2pi radians) needs 0.8 meters to complete, 0.4 meters or 40 cm is just half of it, making a 180º degree phase or 3.14 radians.
Internal energy.
Explanation:
In any substance/object, the particles inside it (atoms/molecules) constantly move in random directions and with random speeds (this motion is called Brownian motion). As a result, the particles have some kinetic energy (which is proportional to the temperature of the substance). Moreover, the particles interact with each other due to the presence of electrostatic intermolecular forces, and as a result, the particles also have some potential energy.
The sum of the kinetic energies and potential energies of the particles in a substance is called internal energy.
<span>Puffins have a predator-prey relationship with salmon.
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Answer:
A regulation game consists of 7 innings unless extended because of a tie score or unless shortened because the home team needs none or only a fraction of its 7th inning or unless 1 team is leading by 10 runs after 5 innings.
Explanation: