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3 years ago

PLEASE HELP ME check the photo.

Physics

1 answer:

ollegr [7]3 years ago

8 0

Answer:

1/ How do scientists determine the elements present in different stars?

KEY WORD for the main idea: Analysis of the starlight.

Answer: Scientists can identify what elements present in different stars by analysing the starlight.

Note: The "starlight" = spectral lines. Astronomers can can identify what kinds of stuff are in stars from the lines they find in star's spectrum. From spectral lines astronomers can determine not only the element, but the temperature and density of that element in the star.

2/ What happens to a star when the fuel for its nuclear fusion reactions is exhausted?

KEY WORD for the main idea: generate light from energy

Answer: A star generates energy through nuclear fusion; this energy is released a light and heat.

Note: The energy source for all stars is nuclear fusion. Stars spend most of their lives repetitively compressing two hydrogen atoms into a single helium atom - plus a lot of energy, which is released as light and heat. A normal star that has exhausted the nuclear fuel in its interior, its outer layers have expanded, and it has become a red giant.

....

3/ Why aren't stars and galaxies spread out evenly across the universe?

KEY WORD for the main idea: Gravitational attraction

Answer: Stars and Galaxies aren't evenly distributed uniformly throughout the universe, because of the existance of gravity.

Note: Gravity, as one of the fundamental forces of the universe, is the powerful force that glues our universe together. This is the one that causes every object in the universe to attract every other object. One of the most noticeable effects of gravity in the solar system is the orbit of the planets.

Explanation:

Hope this answer can help you. Have a nice day !

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michael kicks a ball at an angle if 36* horizontal. its initial velocity is 46 m/s. Find the maximum height it can reach, total

MAVERICK [17]

(a) At its maximum height, the ball's vertical velocity is 0. Recall that

${v_y}^2-{v_{0y}}^2=2a_y\Delta y$

Then at the maximum height $\Delta y=y_{\mathrm{max}}$ , we have

$-\left(\left(46\,\dfrac{\mathrm m}{\mathrm s}\right)\sin36^\circ\right)^2=2\left(-9.8\,\dfrac{\mathrm m}{\mathrm s^2}\right)y_{\mathrm{max}}$

$\implies y_{\mathrm{max}}=37\,\mathrm m$

(b) The time the ball spends in the air is twice the time it takes for the ball to reach its maximum height. The ball's vertical velocity is

$v_y=v_{0y}+a_yt$

and at its maximum height, $v_y=0$ so that

$0=\left(46\,\dfrac{\mathrm m}{\mathrm s}\right)\sin36^\circ+\left(-9.8\,\dfrac{\mathrm m}{\mathrm s}\right)t$

$\implies t=2.8\,\mathrm s$

which would mean the ball spends a total of about 5.6 seconds in the air.

$x=v_{0x}t$

so that after 5.6 seconds, it will have traversed a displacement of

$x=\left(46\,\dfrac{\mathrm m}{\mathrm s}\right)\cos36^\circ(5.6\,\mathrm s)$

$\implies x=180\,\mathrm m$

3 0

2 years ago

If you operate a 2.0 kilowatt for 2 hours how much energy do you use

kap26 [50]

Answer:

4 kWh/day

Explanation:

hope this helps!

~mina-san

3 0

2 years ago

How much heat energy must be added to 52kg Of water at 68°F to raise the temperature to 212°F? The specific heat capacity for wa

Anna [14]

Answer:

The amount of energy added to rise the temperature Q = 17413.76 KJ

Explanation:

Mass of water = 52 kg

Initial temperature $T_{1}$ = 68 °F = 20° c

Final temperature $T_{2}$ = 212 °F = 100° c

Specific heat of water $C = 4.186 \frac{KJ}{kg c}$

Now heat transfer Q = m × C × ( $T_{2}$ - $T_{1}$ )

⇒ Q = 52 × 4.186 × ( 100 - 20 )

⇒ Q = 17413.76 KJ

This is the amount of energy added to rise the temperature.

4 0

2 years ago

A uniform cylindrical grindstone has a mass of 15.0 kg and a radius of 18.6 cm. The grindstone reaches a rotational velocity of

tekilochka [14]

Answer:

$n \approx 5.778\times 10^{-4}\,rev$

Explanation:

The Work-Energy Theorem is applied herein:

$-\frac{1}{4}\cdot m_{cyl}\cdot R^{2}\cdot \omega^{2} = - \mu_{k}\cdot N\cdot r \cdot 2\pi \cdot n$

The number of turns needed to stop the grindstone is:

$n = \frac{m_{cyl}\cdot R^{2}\cdot \omega^{2}}{4\cdot \mu_{k}\cdot N \cdot r\cdot 2\pi}$

$n = \frac{(15\,kg)\cdot (0.186\,m)^{2}\cdot [(1.83\,\frac{rev}{min} )\cdot (\frac{2\pi\,rad}{1\,rev} )\cdot (\frac{1\,min}{60\,s} )]^{2}}{4\cdot (0.80)\cdot (8.82\,N)\cdot(0.186\,m)\cdot 2\pi}$

$n \approx 5.778\times 10^{-4}\,rev$

8 0

3 years ago

Is a

VikaD [51]

Answer:

I believe the answer is D: Conductor.

4 0

3 years ago