Answer:

Explanation:
First of all, we can find the speed of the sound wave, which is given by:

where
f = 645 Hz is the frequency
is the wavelength
Substituting,

Now we can find the temperature of the air by using the following relationship:

where T is the temperature in Celsius degrees. Since we know v = 322.5 m/s, we can re-arrange the formula to find the temperature:

During either one, the sun, moon, and Earth are lined up in the same straight line. The difference is whether the moon or the Earth is the one in the "middle".
Answer: Elastic Potential Energy
Explanation: Energy present on compressed strings is called Elastic Potential Energy.
Answer:
20kg
Explanation:
heat lost by copper=heat gained by watter