Answer:
1.5m
Explanation:
Speed of waves is given as the product of the wavelength and frequency. Sometimes when frequency is not given but the period is given, we get the frequency as the reciprocal of the period. The speed of waves is given in m/s, wavelength in m while frequency in Hz.
Speed, s= fw and making w the subject of formula,

Substituting 300, 000, 000 m/s for s and 200, 000, 000 for f then we obtain that

Answer:
2513.6 W
Explanation:
Acoustic power = sound intensity × area of hemisphere
Sound intensity = 1 W/m^2
Area of hemisphere = 2πr^2 = 2×3.142×20^2 = 2513.6 m^2
Acoustic power = 1 W/m^2 × 2513.6 m^2 = 2513.6 W
Answer : The mass of a sample of water is, 888.89 grams
Explanation :
Latent heat of vaporization : It is defined as the amount of heat energy released or absorbed when the liquid converted to vapor at atmospheric pressure at its boiling point.
Formula used :

where,
q = heat = 2000 kJ =
(1 kJ = 1000 J)
L = latent heat of vaporization of water = 
m = mass of sample of water = ?
Now put all the given values in the above formula, we get:

(1 kg = 1000 g)
Therefore, the mass of a sample of water is, 888.89 grams
B.
carbon dioxide molecules have more energy; therefore, the kinetic energy increases