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
Convection Current
This happens when there is a noteworthy contrast in temperature between two sections of a liquid. At the point when this temperature distinction exists, hot liquids rise and cool liquids sink, and after that streams, or developments, are made in the liquid
Answer:

Explanation:
c = Speed of wave
= Density of medium
A = Area
= Frequency

Intensity of sound is given by

So,

We get

The ratio is 
Answer:
<em>500Joules</em>
Explanation:
Kinetic energy = 1/2mv²
m is the mass of the wood
v is the velocity
Given
Mass = 10kg
Velocity v = 10m/s
Substitute into the formula and get KE
KE = 1/2 * 10 * 10²
KE = 1/2 * 1000
KE = 500Joules
<em>Hence the kinetic energy of the wood during delivery is 500Joules</em>