Answer:
r₂ = 0.2 m
Explanation:
given,
distance = 20 m
sound of average whisper = 30 dB
distance moved closer = ?
new frequency = 80 dB
using formula

I₀ = 10⁻¹² W/m²
now,



to hear the whisper sound = 80 dB



we know intensity of sound is inversely proportional to square of distances



r₂ = 0.2 m
Answer:
Work done is zero
Explanation:
given data
Angle of kite with horizontal = 30 degree
tension in the string = 4.5 N
WE KNOW THAT
Work = force * distance
horizontal force = 
DISTANCE = 0 as boy stands still. therefore
work done = 3.89 *0 = 0
Answer:
3.44 W/m²
1.134 J
Explanation:
E₀ = Intensity of electric field = 50.9 V/m
I = Intensity of electromagnetic wave
Intensity of electromagnetic wave is given as
I = (0.5) ε₀ E₀² c
I = (0.5) (8.85 x 10⁻¹²) (50.9)² (3 x 10⁸)
I = 3.44 W/m²
A = Area = 0.0277 m²
t = time interval = 11.9 s
Amount of energy is given as
U = I A t
U = (3.44) (0.0277) (11.9)
U = 1.134 J
Answer:
685.6 J
Explanation:
The latent heat of vaporization of ammonia is
L = 1371.2 kJ/kg
mass of ammonia, m = 0.0005 Kg
Heat = mass x latent heat of vaporization
H = 0.0005 x 1371.2
H = 0.686 kJ
H = 685.6 J
Thus, the amount of heat required to vaporize the ammonia is 685.6 J.