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Nataliya [291]
3 years ago
9

Radiation makes it impossible to stand close to a hot lava flow. Calculate the rate of heat transfer by radiation, in kW, from 1

.02 m2 of 1000ºC fresh lava into 25.3ºC surroundings, assuming lava’semissivity is 0.97.
Physics
1 answer:
Leya [2.2K]3 years ago
3 0

Answer:

1.5 x 10⁵ W

Explanation:

A = Area of the fresh lava = 1.02 m²

T = Temperature of fresh lava = 1000 °C = 1000 + 273 = 1273 K

T₀ = Temperature of surrounding = 25.3 °C = 25.3 + 273 = 298.3 K

ε = emissivity of the lava = 0.97

σ = stefan's constant = 5.67 x 10⁻⁸ Wm⁻²K⁻⁴

Rate of  transfer is given as

E = σ ε A (T⁴ - T₀⁴)

E = (5.67 x 10⁻⁸) (0.97) (1.02) ((1273)⁴ - (298.3)⁴)

E = 1.5 x 10⁵ W

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What is climate change? How is it caused
OleMash [197]

climate change is a change in climate in the Earth 's normal weather patterns for different climates. it normally changes little by little over the years.the earth is cooler and warming .now it's getting warmer. this phenomenon is also known by as globall warming.it's causes are:

1.energy uses

2.agriculture and land use 3.Transport 4.Industries 5.Growing demands for food and water

A greenhouses is made from glass or clear plastic. It is useful for growing plants in winter in cooler climates.

sorry i don't know last one .

The 2015 United Nations Climate Change Conference, COP 21 or CMP 11 was held in Paris, France, from 30 November to 12 December 2015.

End date: 12 December 2015

Start date: 30 November                                                                       sorry i don't know last one .

Explanation:

8 0
3 years ago
Calculate the work done by a 47N force pushing a pencil against a force of 23 N
stira [4]
I believe the answer would be 24N
Explanation: Because the forces are going against each other, in order to calculate the work done we need to subtract them. 47-23=24
8 0
2 years ago
At cruise conditions, air flows into a jet engine at a steady rate of 60 lbm/s. Fuel enters the engine at a steady rate of 0.59
Amanda [17]

Answer:

ρ=0.0102lbm/ft^3

Explanation:

To solve this problem we must take into account the equation of continuity, this indicates that the sum of the mass flows that enter a system is equal to the sum of all those that leave.

Therefore, to find the mass flow of exhaust gases we must add the mass flows of air and fuel.

m=0.59+60=60.59lbm/s( mass flow of exhaust gases)

The equation that defines the mass flow (amount of mass that passes through a pipe per unit of time) is as follows

m=ρVA

Where

ρ=density

V=velocity

m=mass flow

A=cross-sectional area

solving for density

ρ=m/VA

ρ=60.59/{(1485)(4)}

ρ=0.0102lbm/ft^3

8 0
3 years ago
An object weighs 60.0 kg on the surface of the earth. How much does it weigh 4R from the surface? (5R from the center)
Alecsey [184]
"60 kg" is not a weight.  It's a mass, and it's always the same
no matter where the object goes.

The weight of the object is   

                                 (mass) x (gravity in the place where the object is) .

On the surface of the Earth,

                   Weight = (60 kg) x (9.8 m/s²)

                                =      588 Newtons.

Now, the force of gravity varies as the inverse of the square of the distance from the center of the Earth.
On the surface, the distance from the center of the Earth is 1R.
So if you move out to  5R  from the center, the gravity out there is

                    (1R/5R)²  =  (1/5)²  =  1/25  =  0.04 of its value on the surface.

The object's weight would also be 0.04 of its weight on the surface.

                 (0.04) x (588 Newtons)  =  23.52 Newtons.

Again, the object's mass is still 60 kg out there.
___________________________________________

If you have a textbook, or handout material, or a lesson DVD,
or a teacher, or an on-line unit, that says the object "weighs"
60 kilograms, then you should be raising a holy stink. 
You are being planted with sloppy, inaccurate, misleading
information, and it's going to be YOUR problem to UN-learn it later.
They owe you better material.
6 0
3 years ago
Calculate the momentum of of a 1,5000 kg car traveling at 6 m/s
ANEK [815]

Answer: 90000 kgm/s

Explanation:

Given that,

Momentum of car = ?

Mass of car = 1,5000 kg

Velocity of car = 6 m/s

Recall that momentum is the product of mass of the moving object by its velocity

i.e Momentum = mass x velocity

Momentum = 15000kg x 6m/s

= 90000kgm/s

Thus, the momentum of the car is 90000 kgm/s

4 0
4 years ago
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