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3 years ago

1) How can astronomers determine the chemical composition of stars?

2 answers:

8 0

1. The astronomers can determine the chemical composition of stars by analyzing their emission and absorption as the spectra of the sun and the stars exhibits bright and dark lines are these can be caused by the elements absorbing and emitting light at the specific wavelengths,

2. All objects emit radiation as a result of the growing temperature of the charged particles within the objects as the amount of radiation emitted depends on the temperature of the object.

3. The main components of the Milky Way are:

Disk, bulge and halo.

4. The main difference between the atmospheres of Jupiter and Neptune is that Jupiter has methane clouds.

5. The techniques used to find the exosolar planets are based on An analysis of light.

tatiyna3 years ago

6 0

1). B
2). none of those choices satisfies me
3). B
4). A
5). D

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If a motorcycle accelerates uniformly from rest at 5 m / s2, how long does it take for it to reach a speed of 20 m / s.

irina1246 [14]

Answer:

4 seconds

Explanation:

Given:

v₀ = 0 m/s

v = 20 m/s

a = 5 m/s²

Find: t

v = at + v₀

20 m/s = (5 m/s²) t + 0 m/s

t = 4 s

6 0

3 years ago

· List the atomic numbers of the elements in Period 2.

PilotLPTM [1.2K]

Answer:

3,4,5,6,7,8,9,10

3. lithium

4. beryllium

5. boron

6. carbon

7. nitrogen

8. oxygen

9. fluorine

10. neon

those are the numbers in period 2 on the periodic table.

Explanation:

4 0

2 years ago

Read 2 more answers

Light emitting diode (LEDs) light bulbs have become required in recent years, but do they make financial sense? Suppose a typica

kogti [31]

Answer:

The break even cost is $0.0063825

Explanation:

Break-even cost is the amount of money, or change in value, which equates to the amount at which an asset must be sold to equal the cost of acquiring it. For easier understanding it can be thought the amount of money for which a product or service must be sold to cover the costs of manufacturing or providing it.

Wattage = W

Cost per kilo watt hour = C

Number of hours per year = H

Price per bulb/CFL = P

Discount rate = 11%

Life of bulb = 2 years

Price of bulb = $0.39

Wattage consumption of bulb per hours = 60

Life of CFL = 24 years

Price of CFL = $3.10

Wattage consumption of CFL per hour = 15

Calculate the Equated Annual Cost (EAC) of bulb

EAC = {- P - (W/1000 x H x C) x (PVIFA 11%, 2years)}/ (PVIFA 11%, 2years)

PVIFA 11%, 2years = Annuity PV Factor = [1 – {(1 + r)^(-n)}]/r, where r is the rate per period and n is the number per periods

PVIFA 11%, 2 years = [1 – {(1 + 0.11)^(-2)}]/0.11 = 1.712523 (for 2 years)

PVIFA 11%, 24 years = [1 – {(1 + 0.11)^(-24)}]/0.11 = 8.348136 (for 2 years)

Calculate the EAC of bulb

EAC = {- P - (W/1000 x H x C) x (PVIFA 11%, 2 years)}/ (PVIFA 11%, 2 years)

EAC = {- 0.39 - (60/1000 x H x C) x (1.712523)}/ (1.712523)

EAC = {-0.39 – (51.37570 x C)}/ 1.712523, consider this equation 1

Calculate the EAC of CFL

EAC = {- P - (W/1000 x H x C) x (PVIFA 11%, 24 years)}/ (PVIFA 11%, 24 years)

EAC = {- 3.10 - (15/1000 x 500 x C) x (8.348136)}/ (8.348136)

EAC = {-3.10 – (62.61102 x C)}/8.348137, consider this equation 2

Equate 1 and 2 to find the amount of C

{-0.39 – (51.37570 x C)}/ 1.712523 = {-3.10 – (62.61102 x C)}/8.348137

{-0.39 – (51.37570 x C) x 8.348137} = {-3.10 – (62.61102 x C) x 1.712523}

C = $0.0063825

Thus, the break- even cost per kilo – watt is $0.0063825

3 0

2 years ago

In the process of melting, what best describes what happens to a solid?

Eduardwww [97]

a. A solid will gain kinetic energy and become a liquid.

5 0

2 years ago

Read 2 more answers

Using equations, determine the temperature, pressure and density of the air for a aircraft flying at 19.5 km. Is this aircraft s

Viefleur [7K]

Answer:

a) - 72.5°c

b) pressure = 3625.13 Pa

c) density = 0.063 kg/m^3

d) it is a subsonic aircraft

Explanation:

a) Determine Temperature

Temperature at 19.5 km ( 19500 m )

T = -131 + ( 0.003 * altitude in meters )

= -131 + ( 0.003 * 19500 ) = - 72.5°c

b) Determine pressure and density at 19.5 km altitude

Given :

Po (atmospheric pressure at sea level ) = 101kpa

R ( gas constant of air ) = 0.287 KJ/Kgk

T = -72.5°c ≈ 200.5 k

pressure = 3625.13 Pa

hence density = 0.063 kg/m^3

attached below is the remaining part of the solution

C) determine if the aircraft is subsonic or super sonic

Velocity ( v ) = $\sqrt{CRT}$ = $\sqrt{1.4*287*200.5 }$ = 283.8 m/s

hence it is a subsonic aircraft

4 0

2 years ago