All categories

3 years ago

The spectra of most stars are dark-line spectra because ________.

1 answer:

5 0

Because dark line spectra result from passing white light through ionized gasses and plasmas, which is what the atmosphere of stars are made of. These frequencies are scattered by the star's atmosphere as it leaves the surface (photosphere) of the star, and don't make it to earth.

You might be interested in

The objects listed are placed at the top of a ramp and roll down to the bottom without slipping. Assuming that there is no air r

Thepotemich [5.8K]

Explanation:

For each object, the initial potential energy is converted to rotational energy and translational energy:

PE = RE + KE

mgh = ½ Iω² + ½ mv²

For the marble (a solid sphere), I = ⅖ mr².

For the basketball (a hollow sphere), I = ⅔ mr².

For the manhole cover (a solid cylinder), I = ½ mr².

For the wedding ring (a hollow cylinder), I = mr².

If we say k is the coefficient in each case:

mgh = ½ (kmr²) ω² + ½ mv²

For rolling without slipping, ωr = v:

mgh = ½ kmv² + ½ mv²

gh = ½ kv² + ½ v²

2gh = (k + 1) v²

v² = 2gh / (k + 1)

The smaller the value of k, the higher the velocity. Therefore:

marble > manhole cover > basketball > wedding ring

7 0

3 years ago

Verify that the SI unit of impulse is the same as the SI unit of momentum.

lys-0071 [83]

Maybe this will help you out:

Momentum is calculate by the formula:

$P = mv$

Where:

P = momentum

m = mass

v = velocity

The SI unit:

$mass = kg\\ velocity = \dfrac{m}{s}$

So the unit of momentum would be:

$kg.\dfrac{m}{s}$

Impulse is defined as the change in momentum or how much force changes momentum. It can be calculate with the formula:

I = FΔt

where:

I = impulse

F = Force

Δt = change in time

The SI unit:

F = Newtons (N) or $kg.\dfrac{m}{s^{2} }$

t = Seconds (s)

So the unit of impulse would be derived this way:

I = FΔt

I = $kg.\dfrac{m}{s^{2} }$ x $s$

$\dfrac{kg.m.s}{s^{2}} = \dfrac{kg.m.s}{s.s}$

You can then cancel out one s each from the numerator and denominator and you'll be left with:

$kg.\dfrac{m}{s}$

So then:

Momentum: Impulse

$kg.\dfrac{m}{s}$ $kg.\dfrac{m}{s}$

4 0

3 years ago

Two coils of wire are placed close together. Initially, a current of 3.04 A exists in one of the coils, but there is no current

Alchen [17]

Answer:

$M=0.0247H$

Explanation:

Given data

$V_{voltage}=4.29V\\I_{current}=3.04A\\t_{time}=1.75*10^{-2}s$

To find

Mutual inductance of the two-coil system

Solution

The mutual inductance given as:

M= (-VΔt)/ΔI

Substitute the given values

$M=-\frac{4.29V*1.75*10^{-2}s}{(0-3.04A)}\\ M=0.0247H$

4 0

3 years ago

You make a straight line when an object is

swat32

Answer:

can you explain more or..,.

Explanation:

8 0

3 years ago

Read 2 more answers

The temperature of a solution will be estimated by taking n independent readings and averaging them. Each reading is unbiased, w

Viktor [21]

Answer:

68 readings.

Explanation:

We need to take this problem as a statistic problem where the normal distribution table help us.

We can start considerating that X is the temperature of the solution, then

$0.9 = P(|\bar{x}-\mu|$

$0.9 = P(\frac{|\bar{x}-\mu|}{\frac{\sigma}{\sqrt{n}}}$

$0.9 = P(|Z|$

For a confidence level of 90% our $Z_{critic}$ is 1.645

Therefore,

$\frac{0.1}{\frac{\sigma}{\sqrt{n}}} = 1.645$

Substituting for $\sigma = 5$ and re-arrange for n, we have that n is equal to

$n=(\frac{1.645\sigma}{0.1})^2$

$n=\frac{(1.645)^2(0.5)^2}{0.1^2}$

$n=67.65$

$n=68$

We need to make 68 readings for have a probability of 90% and our average is within $0.1\°\frac$

3 0

2 years ago