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2 years ago

Which of the following has the lowest U value?

Physics

1 answer:

jarptica [38.1K]2 years ago

4 0

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

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If a person weighs 818 N on earth and 5320 N on the surface of a nearby planet, what is the acceleration due to gravity on that

alexandr402 [8]

Answer:

$g'=63.74\ m/s^2$

Explanation:

It is given that,

Weight of the person on Earth, W = 818 N

Weight of a person is given by the following formula as :

$W=mg$

g is the acceleration due to gravity on earth

$m=\dfrac{W}{g}$

$m=\dfrac{818\ N}{9.8\ m/s^2}$

m = 83.46 kg

The mass of an object is same everywhere. It does not depend on the location.

Let W' is the weight of the person on the surface of a nearby planet, W' = 5320 N

g' is the acceleration due to gravity on that planet. So,

$g'=\dfrac{W'}{m}$

$g'=\dfrac{5320\ N}{83.46\ kg}$

$g'=63.74\ m/s^2$

So, the acceleration due to gravity on that planet is $63.74\ m/s^2$ . Hence, this is the required solution.

6 0

2 years ago

Assuming the pick-up trucks, trailers and road conditions are exactly the same, which vehicle will take a longer distance to sto

mars1129 [50]

I’ve answered this before so I know the question is missing an important given and that given is: 1 has an empty trailer and the other has a fully loaded one.

So, it would be the fully loaded trailer that would take a longer distance to stop because a lot of weight is being pulled, and when the brakes are started, the fully loaded trailer is more like pushing against the truck.

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2 years ago

Cold butter placed on hot corn melts because of convection. agree disagree it depends

frozen [14]

Explanation:

Cold butter placed on hot corn melts because of convection. Butter placed on hot corn melts because it touches the hot corn. Most of the heat is transferred through conduction

7 0

3 years ago

A person throws a pumpkin at a horizontal speed of 4.0 — off a cliff. The pumpkin travels 9.5 m horizontally

emmainna [20.7K]

Complete Question

A person throws a pumpkin at a horizontal speed of 4.0 m/s off a cliff. The pumpkin travels 9.5m horizontally before it hits the ground. We can ignore air resistance.What is the pumpkin's vertical displacement during the throw? What is the pumpkin's vertical velocity when it hits the ground?

Answer:

The pumpkin's vertical displacement is $H = 27 .67 \ m$