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4 years ago

11

How long does it take the sun to melt a block of ice at 0âc with a flat horizontal area 1.0 m2 and thickness 1.8 cm ? assume tha

t the sun's rays make an angle of 37 â with the vertical and that the emissivity of ice is 0.050?

1 answer:

snow_lady [41]4 years ago

3 0

At least 20-30 seconds

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A car with a constant velocity of 22 m/s is driven for 6.8 s. How far did it travel? (V =A d/AT)

SVEN [57.7K]

Answer: 150 m

Explanation:

velocity = 22 m/s

t = 6.8 s

velocity = $\frac{distance}{time}$

distance = velocity × time

= 22 × 6.8

= 149.6 m

≈ 150 m

option C

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3 years ago

Kik wants to cook popcorn on the stove. What type of energy will she be using

Y_Kistochka [10]

Electrical and thermal

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3 years ago

Read 2 more answers

Problems related to radiation. (a) The temperature of the Sun’s photosphere is 5700 K. Assume it is a blackbody. What is the pea

sineoko [7]

Answer:

a) λ = 5,084 10⁻⁷ m , b) P = 3.63 10²⁶ W , c) P = 5.8 10²⁷ W and d) λ = 2.54 10⁻⁷ m

Explanation:

a) The maximum emission of the sun can be calculated using the Win equation

λ T = 2,898 10⁻³ m.K

λ = 2,898 10⁻³ / T

λ = 2,898 10⁻³ / 5700

λ = 5,084 10⁻⁷ m

λ = 5,084 10⁻⁷ m (1 10⁹ nm / 1m) =

λ = 5,084 10² nm = 508.4 nm

photon in the visible range

b) The emission of the Sun, is described by the Stefan equation

P = σ A e T⁴

Where σ is the Stefan-Boltzmann constant that vslue is 5,670 10-8 W/m²K⁴, A area of the Sun, and e the emissivity that for a perfect black body is 1

In order to use this equation, we must calculate the area of the sun, we consider it a perfect sphere

r = 695,000 km (1000m / 1 km) = 6.95 10⁸ m

Area of a sphere

A = 4π R²

A = 4π (6.95 10⁸8)²

A = 6.07 10¹⁸ m²

P = 5,670 10⁻⁸ 6.07 10¹⁸ 1 5700⁴

P = 3.63 10²⁶ W

c) The new temperature is double the previous one

T = 2 To

Let's substitute in the formula and calculate

P = σ A e (2To)⁴

P = σ A e T⁴ 2⁴

Po = σ A e T4 = 3.63 10 26 W

P = 16 Po

P= 16 (3.63 10²⁶)

P = 5.8 10²⁷ W

d) Let's calculate the explicit value of the temperature and use the Win equation

T = 2 5700

T = 11400K

λ = 2,898 10⁻³ / 11400

λ = 2.54 10⁻⁷ m

λ = 2.54 10²nm = 254 nm

photon in the UV range

5 0

3 years ago

If several forces are exerted on a system, calculate the work done by each force, then multiply the results.

maria [59]

Answer:

false, each force might have a different about and a different direction

4 0

4 years ago

A rock of mass m is twirled on a string in a horizontal plane. The work done by the tension in the string on the rock is..

anyanavicka [17]

Answer:

work done by tension force on the twirled stone must be ZERO always

Explanation:

As we know that work done by a force on an object is given as

$W = F.d$

$W = Fdcos\theta$

here we know that

$\theta$ = angle between force and displacement

now we know that tension in the string and displacement of the object is always perpendicular to each other when the rock is twirled in circular path.

so we can say for this motion of the stone

$cos\theta = 0$

so work done by tension force on the twirled stone must be ZERO always

6 0

3 years ago