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
Answer:
answer is option (c) child labour
The combined momentum is 4000 kg m/s south
Explanation:
The total combined momentum of the two cars is given by the vector addition of the momenta of the two cars.
For this problem, we choose north as positive direction and south as negative direction.
The momentum of the first car travelling north is given by:
where
is the mass of the car
is its velocity
Substituting,
The momentum of the second car travelling south is given by:
where
is the mass of the car
is its velocity (negative because the car travels south)
Substituting,
And therefore, the combined momentum is
where the negative sign means the direction of the total momentum is south.
Learn more about momentum:
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The centripetal force is provided by the friction between the tyres and the ground. That's why a car will slip on ice, because there is less friction.
let the height of the person with marshmallow on her head be "h"
consider the motion of the marshmallow after it is dropped from bridge.
Y₀ = initial position of the marshmallow above the ground = 5.71 m
Y = final position of marshmallow on head of person = h
v₀ = initial velocity of the marshmallow = 0 m/s
a = acceleration due to gravity = - 9.8 m/s²
t = time of travel for marshmallow = 0.921 sec
Using the kinematics equation
Y = Y₀ + v₀ t + (0.5) a t²
inserting the values
h = 5.71 + 0 (0.921) + (0.5) (-9.8) (0.921)²
h = 5.71 - 4.16
h = 1.55 m
