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3 years ago

The phrase "hot air rises" describes which type of heat transfer?

Physics

2 answers:

yan [13]3 years ago

7 0

hot air rises is conduction heat transfee

77julia77 [94]3 years ago

5 0

Answer:

Option C

Explanation:

C. Convection...

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Part A: Determine the wavelength of photons that can be emitted

torisob [31]

Answer:

A λ = 97.23 nm

, B) λ = 486.2 nm

, C) λ = 53326 nm

Explanation:

With that problem let's use the Bohr model equation for the hydrogen atom

$E_{n}$ = -k e² /2a₀ 1/n²

For a transition between two states we have

$E_{nf}$ - $E_{no}$ = -k e² /2a₀ (1/ $n_{f}$ ² - 1 / n₀²)

Now this energy is given by the Planck equation

E = h f

And the speed of light is

c = λ f

Let's replace

h c / λ = - k e² /2a₀ (1 / $n_{f}$ ² - 1 / no₀²)

1 / λ = - k e² /2a₀ hc (1 / $n_{f}$ ² -1 / n₀²)

Where the constants are the Rydberg constant $R_{H}$ = 1.097 10⁷ m⁻¹

1 / λ = $R_{H}$ (1 / n₀² - 1 / nf²)

Now we can substitute the given values

Part A

Initial state n₀ = 1 to the final state $n_{f}$ = 4

1 / λ = 1.097 10⁷ (1/1 - 1/4²)

1 / λ = 1.0284 10⁷ m⁻¹

λ = 9.723 10⁻⁸ m

We reduce to nm

λ = 9.723 10⁻⁸ m (10⁹ nm / 1m)

λ = 97.23 nm

Part B

Initial state n₀ = 2 final state $n_{f}$ = 4

1 / λ = 1.097 10⁷ (1/2² - 1/4²)

1 / λ = 0.2056 10⁻⁷ m

λ = 486.2 nm

Part C

Initial state n₀ = 3

1 / λ = 1,097 10⁷ (1/3² - 1/4²)

1 / λ = 5.3326 10⁵ m⁻¹

λ = 5.3326 10-5 m

λ = 53326 nm

5 0

3 years ago

Julie drives 100 mi to Grandmother's house. On the way to Grandmother's, Julie drives half the distance at 20 mph and half the d

Gnoma [55]

Answer:

On the way to grandmother´s, the average speed was 30 mph. On the way back, the average speed was 40 mph.

Explanation:

The average speed is given by the variation of the position over time.

Mathematically:

ΔX / Δt = v

where:

ΔX = distance (final position - initial position)

Δt = time (final time - initial time)

v = speed

On the way to Grandmother´s, we can calculate how much time Julie drove at each speed:

ΔX / Δt = v

ΔX / v = Δt

50 mi / 20 mph = 2.5 h

In the same way, we can calculate how much time she drove at 60 mph:

50 mi / 60 mph = 0.83 h

In total, she drove a distance of 100 mi in (2.5 h + 0.83 h) 3.33 h. Then, the average speed on the way to Grandmother´s was:

In the return trip, we do not know the distance nor the time that she drove at each speed, but we know that for each part of the trip, the time is the same (Δt) and we also know that the total distance is 100 mi and the total time is 2Δt:

v1 = ΔX1 / Δt

v2 = ΔX2 / Δt

ΔX2 + ΔX1 = 100

where

v1 = speed during the first part of the trip (20 mph)

v2 = speed during the second part of the trip (60 mph)

ΔX1 = distance driven at 20 mph

ΔX2 = distance driven at 60 mph

Δt = time

If we divide v2/v1, we will get:

v2/v1 = (ΔX2 / Δt) / (ΔX1 / Δt)

60 mph / 20 mph = ΔX2 / ΔX1

3 = ΔX2 / ΔX1

3ΔX1 = ΔX2

Then we can replace ΔX2 for 3ΔX1 in this equation:

ΔX2 + ΔX1 = 100 mi

3ΔX1 + ΔX1 = 100 mi

4ΔX1 = 100 mi

ΔX1 = 25 mi

And now, we can solve Δt from the equation of v1:

v1 = ΔX1 / Δt

Δt = ΔX1 / v1 = 25 mi / 20 mph = 1.25 h

The average speed on the return trip is then:

8 0

4 years ago

Which of the following is NOT a symptom associated with hypertension?

zepelin [54]

I would say a or d hope this helps haha ( also if you could do brainliest for this that would be AMASINF bc I really want to rank up, u don’t have to tho)

8 0

3 years ago

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How to make green colour with two colours?

butalik [34]

Blue and yellow make green

5 0

3 years ago

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n noisy factory environments, it's possible to use a loudspeaker to cancel persistent low-frequency machine noise at the positio

lys-0071 [83]

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