Answer:
About 133 db.
Explanation:
Sound Intensity Level in db (SIL db) is equal to 10log (base 10) times the ratio of the sound intensity at 200 watts (I) relative to the sound intensity of the reference sound intensity (I sub 0), which by default is equal to 10⁻¹² W/m² or 0 dB.
I = 200 w / 10 m^2 = 20 w per square meter
I sub 0 = 10^-12 w per square meter
SIL = 10log ( I / I sub o) = 20 / 10^-12 = 10log ( 20^12) = 10 ( 13.3 ) = 133 db
Hope I typed this part correctly. Hard to get it in without being able to do exponents, etc. :D
<h2>
Option C is the correct answer.</h2>
Explanation:
Specific gravity of fluid = 0.750
Density of fluid = Specific gravity of fluid x Density of water
Density of fluid = 0.750 x 1000
Density of fluid = 750 kg/m³
Mass of fluid = 22.5 kg
We have
Mass = Volume x Density
22.5 = Volume x 750
Volume = 0.03 m³ = 30 L
Option C is the correct answer.
Answer:
c. expanded polyurethane
Explanation:
Thermal performance of a building fabric is measured in terms of heat loss and is expressed as U-value or R-value. U-value is the rate of heat transferred through a structure divided by the difference in temperature across the structure with a unit of measurement of W/m²K.You can calculate the U-value of a by getting the reciprocal of the sum of thermal resistances , R, making the building material.
If you have the value of R, then U=1/R
Material size R U
plywood 1" 1.25 0.8
Poured concrete 2" 0.99 1.010
Expanded polyurethane 1" 6.5 0.1538
Asbestos shingles 1" 0.03 33.33
The material with lowest U-value is expanded polyurethane
Carbon: C, 12.011, 6, 12
Oxygen: O, 8, 8, 8, 16
Boron: B, 10.811, 5, 5, 11
