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andreev551 [17]
4 years ago
14

Eva is in a closed, dark room. She uses her arm muscles to turn on a lamp. When she moves her hand closer to the lamp, the light

heats her hand. The light bounces off the pages of a book and into her eyes.
If this room is a closed system, what happens to the total amount of energy in the room?

A.
It remains constant.

B.
It decreases.

C.
It increases, then decreases.

D.
It increases.
Physics
2 answers:
guapka [62]4 years ago
5 0
Its a tricky one but my guess would be D if she turned on the lamp causing energy if would have increased the amount in the specificed room x
12345 [234]4 years ago
4 0

Well, we know that the total energy in a closed system remains constant.

The problem with the story of Eva is that she is not in a closed system. 
If the dark room were really a closed system, then she could press the
button or turn the switch all day, and the lamp could not light.  It needs
electrical energy coming in from somewhere in order to turn on.

Let's say that Eva used her arm muscles to strike a match and light the
candle on the table.  Then we would have have food energy, muscle
energy, chemical energy in the match, chemical energy in the candle,
heat and light energy coming out of the candle, heat energy soaking into
her hand, light energy bouncing off of the book and into her eyes ... all
going on during the story, and the sum total of all of them would remain
constant.
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What causes the difference in the angle of the sun on the Earth's surface throughout the year?
Novosadov [1.4K]

Answer:

The axis is tilted and points to the North Star no matter where Earth is in its orbit. Because of this, the distribution of the Sun's rays changes. ... It also means that the angle at which sunlight strikes different parts of Earth's surface changes through the year.

Explanation:

Pls sub to bdoggaming if this helped

5 0
3 years ago
Escape velocity of an object from the surface of a planet depends upon:
andrey2020 [161]

Answer:

Escape velocity: Measuring the gravitational strength of an object

The escape velocity is the exact amount of energy you would need to escape the gravitational clutches of an object with mass. Since all objects have mass, they all have a measureable gravitational strength. A good way to think about escape velocity is to think about a deep well (physicists like to think of this as an energy well). If you are at the bottom of the well and want to get out (to escape), you need enough energy to climb out. The deeper the well, the more energy you will have to expend in order to climb to

the top. If you have only enough energy to get half way out, you will eventually fall back to the bottom. The escape velocity is a way of measuring the exact amount of energy needed to reach the lip of the well -- and have no energy left over for walking away.

When a ball is thrown up into the air from the surface of the Earth, it does not have enough energy to escape. So it falls back down. How might we enable the ball to escape? Throw it harder, give it more energy. How hard must we throw it? Just hard enough to get over the top, over the edge of the well.

We can find this energy directly by saying that the kinetic energy of the thrown ball must exactly equal the 'potential energy' of the well. From basic physics we know that the potential energy for an object at a height above a surface is:

Epotential= GMm/R

where

G = Newton's universal constant of gravity = 6.67 x 10-11 N-m2/kg3

M = the mass of the 'attracting object' [the planet] [in units of kg]

m = the mass of the object trying to escape [e.g., me or a ball or a rocket or a molecule] [in kg]

R = the distance between the centers of objects M and m [in units of m]

note: provided we do everything in the same units, we don't have to worry about units

while the kinetic energy we know from above:

Ekinetic=0.5 m v2

where

m = mass of the moving object [in kg]

v = the velocity of object m [in m/sec]

If we set these two energies equal to each other, and solve for v, we find the exact velocity needed to escape from the energy well:

0.5 m v2= GMm/R

v= (2GM/R)0.5

and since this velocity is exactly what is needed to 'escape,' it is called the escape velocity:

vescape= (2GM/R)0.5

Explanation:

that's my all i know

correct me if I'm wrong❤️

7 0
2 years ago
If Tony and Tanya both run at the same speed and in the same direction and they both run for the same amount of time, what can y
Marina86 [1]

Answer: They travel equal distances

Explanation:

Distance is amount of space covered from one point to another. It is measured in metres. Distance = speed x time taken

In this case,

- Since Tony and Tanya both run at the same speed: let speed = b

- Also, both run for the same amount of time: let time = c

Therefore, distance covered by Tony and Tanya = speed x time taken

Distance = b x c

Distance = bc (i.e Tony travelled a distance of bc, so also Tanya)

8 0
3 years ago
Please help me fast
MakcuM [25]

Answer:

b I think. sorry if it's wrong

6 0
3 years ago
What is frequency of light is emitted when an electron jumps into the smallest orbit of hydrogen, coming from a very large radiu
mrs_skeptik [129]

Answer:

3.28403\times 10^{15}\ Hz

Explanation:

n_1 = 1

n_2=\infty

h = Planck's constant = 6.626\times 10^{-34}\ m^2kg/s

The energy is given by

E(n)=E_1(\dfrac{1}{n_1^2}-\dfrac{1}{n_2^2})\\\Rightarrow E(1)=13.6\ eV

Energy is also given by

E=hf\\\Rightarrow f=\dfrac{E}{h}\\\Rightarrow f=\dfrac{13.6\times 1.6\times 10^{-19}}{6.626\times 10^{-34}}\\\Rightarrow f=3.28403\times 10^{15}\ Hz

The frequency of light emitted would be 3.28403\times 10^{15}\ Hz

7 0
3 years ago
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