The key insight that Bohr introduced to his model of the atom was that the angular momentum of the electron orbiting the nucleus was quantized. He introduced the postulate that the angular momentum could only come in quantities of nh/(2π), where h is Planck's constant and n is a nonnegative integer (0,1,2,3,…). Given this postulate, what are the allowable values for the velocity v of the electron in the Bohr atom? Recall that, in circular motion, angular momentum is given by the formula L= mvr.
Answer:
v = [tex]n \frac{\hbar }{m r}[/tex]
the sppedof the electron is also quantized
Explanation:
The angular momentum of a rotating body is
L = m v r
in Bohr's atomic model the quantization postulate is that the angular momentum is equal to
L = n [tex]\hbar[/tex]
we substitute
n [tex]\hbar[/tex] = m v r
v = [tex]n \frac{\hbar }{m r}[/tex]
where n is an integer.
Therefore, the sppedof the electron is also quantized, that is, sol has some discrete values.
The shape of the orbit for most comets is a(n):
circle
parabola
ellipse
oval
Answer:
Ellipse
Explanation:
Most comets have an elliptical path of orbit.
Answer: The shape of the orbit for most comets is: ellipse
You are exploring a small moon of a distant planet. Measurements indicate that this moon is a sphere of uniform density rho = 5000 kg/m3. You dig a very deep hole into the moon that reaches within r0 = 1000 m of the center of the moon. With your spacesuit, you have a mass of m = 85 kg. Find the force of gravity on you when you stand at the bottom of the hole.
Answer:
The force of gravity will be "0.11874 N"
Explanation:
The given values are:
Density of planet,
Q = 5000 Kg/m³
Inside radius,
r₀ = 1000 m
Now,
The mass of inside sphere will be:
⇒ [tex]m_p=density\times volume[/tex]
⇒ [tex]=5000\times \frac{4}{3}\pi r^3[/tex]
On putting the values, we get
⇒ [tex]=5000\times \frac{4}{3}\times \pi\times (1000)^3[/tex]
⇒ [tex]=85 \ kg[/tex]
hence,
The force of gravity will be:
= [tex]\frac{Gm_{planet} m_{person}}{r^2}[/tex]
= [tex]\frac{6.67\times 10^{-11}\times 5000\times 4\pi\times 85\times 1000}{3}[/tex]
= [tex]\frac{6.67\times 10^{-11}\times 4\pi\times 425000000}{3}[/tex]
= [tex]0.11874 \ N[/tex]
How does the excretory system work with the circulatory system to help the body regulate itself?
Answer:
The excretory system is a close partner with both the circulatory and endocrine system. The circulatory system connection is obvious. Blood that circulates through the body passes through one of the two kidneys. Urea, uric acid, and water are removed from the blood and most of the water is put back into the system.
Explanation:
A spool whose inner core has a radius of 1.00 cm and whose end caps have a radius of 1.50 cm has a string tightly wound around the inner core. The spool is free to roll without slipping on a horizontal surface. If the string unwinds horizontally from the bottom of the core with a constant speed of 25.0 cm/s, what is the speed of the spool
Answer:
v₁ = 37.5 cm / s
Explanation:
For this exercise we can use that angular and linear velocity are related
v = w r
in the case of the spool the angular velocity for the whole system is constant,
They indicate the linear velocity v₀ = 25.0 cm / s for a radius of r₀ = 1.00 cm,
w = v₀ /r₀
for the outside of the spool r₁ = 1.5 cm
w = v₁ / r₁1
since the angular velocity is the same we set the two expressions equal
[tex]\frac{v_o}{r_o} = \frac{v_1}{r_1}[/tex]
v1 = [tex]\frac{r_1}{r_o} \ \ v_o[/tex]
let's calculate
v₁ = [tex]\frac{1.50}{1.00} \ \ 25.0[/tex]
v₁ = 37.5 cm / s
when the friction increases too much does the object stay still or moving opposite direction
Answer:
the moment when the object starts to move
Answer:
The object stays still when there is too much friction applied to the equation with the mass and applied force.
Explanation:
Penn Foster
Show that if you have three polarizing filters, with the second at an angle of 45 degrees to the first and the third at an angle of 90 degrees to the first, the intensity of light passed by the first will be reduced to 25% of its value. (This is in contrast to having only the first and third, which reduces the intensity to zero, so that placing the second between them increases the intensity of the transmitted light.)
Answer:
I₃ /I₀ = 25%
Explanation:
For this exercise let's use Malus's law
I = I₀ cos² θ
where tea is the angle between the two polarizers.
When the polarized light passes the first polarizer, the intensity is constant if it is in the direction of polarization.
I₁ = I₀
the light transmitted by the second polarizer is
I₂ = I₁ cos² θ
I₂ = I₀ cos² 45
I₂ = I₀ 0.5
this light is polarized 45º with respect to the first polarizer
Now let's examine the third polarizer, it is indicated that it has an angle of 90º with respect to the first polarizer, the angle with respect to the second polarizer is
θ = 90 - 45
θ = 45º
so the polarizer is at an angle of 45º
let's use Maus's law
I₃ = I₂ cos² 45
I₃ = I₀ 0.5 cos² 45
I₃ = I₀ 0.25
the light that passes through the system is
I₃ /I₀ = 0.25
as a percentage we multiply by 100
I₃ /I₀ = 25%
Light is traveling in glass, and hits a glass/unknown surface. In the glass the light beam is making an angle of 45.0 o with the normal to the surface. The glass has an index of refraction of 1.52. (A) If the refracted light ray leaves the glass at an 55o from the normal, what is the index of refraction for the unknown surface
Answer:
n = 1.31
Explanation:
When a ray of light crosses the separation surface between two transparent media, there exists a fixed relationship between the indexes of refraction of both media, related with the angles of incidence and refraction, which is known as Snell's Law.The Snell's Law can be written as follows:[tex]n_{i} * sin( \theta_{i}) = n_{r} * sin( \theta_{r}) (1)[/tex]
In our case the ray is incident from the glass, so ni = n glass = 1.52The angle of incidence is the angle that the ray makes with the normal to the separation surface, so θi=45º.The angle of refraction is the angle that the refracted ray makes with the normal, so θr= 55ºReplacing by the values in (1), and solving for nr, we have:[tex]n_{r} =\frac{n_{i} * sin \theta_{i} }{sin \theta_{r} } = \frac{sin (45)*1.52}{sin (55)} = 1.31 (2)[/tex]
1
1 point
The table shows the lengths and diameters of four copper wires.
Which wire has the least resistance?
length/m
diameter/mm
A
0.50
1.0
B
0.50
2.5
С
0.75
1.0
D
0.75
2.5
А
B
D
Answer:
where is the table?????????
The wire has a length of 0.50 m and a diameter of 2.5 mm and has the least resistance, so, option B is correct.
What is resistance?A substance's ability to obstruct the flow of electrical current is referred to as resistance. It is symbolized by the capital letter R. The ohm, frequently written as a word and sometimes represented by the capital Greek letter omega, is the unit of resistance that is typically used.
Given:
The length of the wire A = 0.50 m and the diameter is 1 mm,
The length of the wire B = 0.50 m and the diameter is 2.5 mm,
The length of the wire C = 0.75 m and the diameter is 1 mm,
The length of the wire D = 0.75 m and the diameter is 2.5 mm,
Calculate the L / Area factor of all the wires as shown below,
L / Area factor of A = 0.50 / π × 0.0005²
L / Area factor of A = 636619.8
L / Area factor of B = 0.50 / π × 0.00125²
L / Area factor of B = 101859
L / Area factor of C = 0.75 / π × 0.0005²
L / Area factor of C = 955414
L / Area factor of D = 0.75 / π × 0.00125²
L / Area factor of D = 152866
As we can see, if the L / Area factor of B is less, then its resistance will be the least.
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Convert 125 mL to L
Answer:
1 L = 1000 mL
125 mL = 125/1000 = 0.125 L
Answer:
0.125
Explanation:
divide by 1 000 to convert mL to liters
94. The diagram shows the orbit of a satellite
around Earth. If Earth's mass is 5.97x10 kg,
what is the satellite's orbital speed?
(G=6.67x10-11 N·mº/kg?)
A 5.84x10' m/s
B 6.31x104 m/s
C 7.23x10 m/s
D 7.65x10 m/s
Answer:
7.65x10^3 m/s
Explanation:
The computation of the satellite's orbital speed is shown below:
Given that
Earth mass, M_e = 5.97 × 10^24 kg
Gravitational constant, G = 6.67 × 10^-11 N·m^2/kg
Orbital radius, r = 6.80 × 10^6m
Based on the above information
the satellite's orbital speed is
V_o = √GM_e ÷ √r
= √6.67 × 10^-11 × 5.97 × 10^24 ÷ √6.80 × 10^6
= 7.65x10^3 m/s
A teacher gives students a sunglasses lens and asks them to observe the surface of a pond on a sunny day. The students notice that the water on the surface of the pond appears brighter and then dimmer when they rotate the lens as they look through it at the pond. The teacher asks the students to explain this observation. Which of the following student statements provides a correct explanation?
A. The lenses of the sunglasses absorb and transmit light of different wavelengths or offerent angles of lens rotation, thus transmitting more or less light to our eyes
B. Rotating the sunglasses changes the index of retraction of the lenses, co more light is tetracted away from our eyes at some angles
C. Only some of the light is reflected from the surface of the pond and rotating the lens causes more or less light to be transmitted at some angles
D. The light is linearly polarized when it is reflected off the surface of the pond, and the lens is a polariangles that transmits more light at certain angles
Answer:
Option D
Explanation:
Option (A) is incorrect because transmission of few wavelength will procure visibility of only few colours and not all. Option B is also incorrect as refraction index remains same as it does not changes with the change in angle. Option C is also incorrect because changing orientation of only some of the light with not make any significant difference
Option D is correct because sunlight is a unpolarised light which can be polarised using reflection. Now when sunlight gets partially linearly polarized after reflection from the lake, it can be viewed by the observer's eye through the lens.
B is the statements provide is a correct explanation. Rotating the sunglasses changes the index of refraction of the lenses, so more light is retracted away from our eyes at some angles.
What is a refractive index?The refractive index n is defined as the ratio of the sine of the incidence angle to the sine of the refraction angle, i.e., n = sin I / sin r.
The velocity of light c of a given wavelength in empty space divided by its velocity v in a substance, or n = c/v, is also equal to the refractive index.
Rotating the sunglasses changes the index of refraction of the lenses, so more light is retracted away from our eyes at some angles.
Hence option B is correct.
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How are both electromagnetic and mechanical waves used when people communicate with each other?
How does competition affect population size? Use the terms carrying capacity and limiting factor with your example.
Limiting factors are resources or other factors in the environment that can lower the population growth rate. Competition for resources like food and space cause the growth rate to stop increasing, so the population levels off. This flat upper line on a growth curve is the carrying capacity.
Answer:
they can eat all of the food and kill off the population
Explanation:
if the competition eats all of the food there's no food for the population and they will die off.
Stars that are not very hot but give off a lot of light are
O nebula
O main sequence stars
giants
O giants
O dwarfs
[tex]\huge{\textbf{\textsf{{\color{navy}{An}}{\purple{sw}}{\pink{er}} {\color{pink}{:}}}}}[/tex]
Giants.
thankshope it helps.Explanation:
giants are those stars that are not so hot but give a lot of light
4. A 9000 kg train car travelling at 4.5 m/s inellastically collides with a 7500 kg train car at rest. If
all of the kinetic energy not conserved in this collision goes into increasing the internal energy of
the cars, how many Joules were absorbed?
Answer:
91125Joules
Explanation:
Given data
M1= 9000 kg
U1= 4.5m/s
M2= 7500 kg
U1= 0 m/s
KE1= 1/2M1U1^2
KE1= 1/2*9000*4.5^2
KE1= 1/2*9000*20.25
KE1= 1/2*182250
KE1=91125joules
KE2= 1/2M2U2^2
KE1= 1/2*7500*0^2
KE1=0 joules
Hence the energy absorbed is
E= KE1-KE2
E= 91125-0
E= 91125Joules
PLEASE HURRY I GIVE BRAINLIEST AND EXTRA POINTS !!!
Prompt: How does melanin provide protection against skin cancer?
Read and annotate the second paragraph of the "What Is Melanin?" article, then write an
explanation of how this evidence helps answer the question. Use the following words in your
explanation: absorb, energy, light.
Answer:
Melanin is a protective pigment in skin, blocking UV radiation from damaging DNA and potentially causing skin cancer. Melanin does protect us, but this research shows it can also do us harm.
Definition:
UVA radiation causes lesions or DNA damage to melanocytes, which are the skin cells that produce the skin pigment known as melanin.
Explanation:
Melanin is a pigment that is produced by cells known as melanocytes in the skin of most animals, including humans. This pigment comes in different shades, depending on the genetic makeup of the individual. Melanin comes in two basic forms and can range from yellowish-red to dark brown. Eumelanin is the most common form of melanin and is brownish in color. The other basic form is called pheomelanin, which produces reddish-brown color that is often associated with freckles and red hair. The production of melanin in the individual is determined by several factors.
Genetically speaking, every individual on Earth has approximately the same number of melanocytes. The difference, then, in the production of melanin is affected by:
Exposure to UV radiation: Melanin is produced as a response to UV radiation in order to prevent damage to the DNA in the integument. Individuals, who are exposed to UV light, such as the sun, will produce more melanin for protection.
Genetic makeup: Different ethnicities and cultures are genetically pre-disposed to producing particular shades and amounts of melanin due to inheritance. This is, essentially, one of the primary indicators used in determining race in the human population. It is important to note that this is, and has historically been, a controversial form of human identification.
Size of melanocytes: Melanocyte size varies in different individuals and may lead to a difference in the amount of melanin produced per cell.
Disease conditions: Several diseases may affect melanin production, including albinism, a genetic inability to produce melanin, and vitiligo, a progressive loss of melanocytes.
A 10 kg medicine ball is thrown at a velocity of 15 km/hr ( m/s) to a 50 kg skater who is
at rest on the ice. The skater catches the ball and subsequently slides with the ball across the
ice.
Complete Question
A 10 kg medicine ball is thrown at a velocity of 15 km/hr ( m/s) to a 50 kg skater who is at rest on the ice. The skater catches the ball and subsequently slides with the ball across the ice.
Calculate the kinetic energy after collision(in joules).
Answer:
[tex]K.E=70.23J[/tex]
Explanation:
From the question we are told that:
Mass of ball [tex]m_b=10kg[/tex]
Speed [tex]V_{b1}=15 km/hr ( m/s)[/tex]
[tex]V_{b1} = 4.1667 m/s[/tex]
[tex]V_{b1} = 4.1667 m/s[/tex]
Mass of Skater [tex]m_s=50kg[/tex]
Generally the equation for conservation of momentum is mathematically given by
[tex]m_sV_{s1}+m_bV_{b1}=(m_s+m_b)V[/tex]
[tex]V=\frac{m_sV_{s1}+m_bV_{b1}}{(m_s+m_b)}[/tex]
[tex]V=\frac {50+10*4.1667}{(50+10)}[/tex]
[tex]V=1.53m/s[/tex]
Generally the equation for Kinetic energy is mathematically given by
[tex]K.E=\frac{1}{2}(m_s+m_b)V^2[/tex]
[tex]K.E=\frac{1}{2}(50+10)(1.53)^2[/tex]
[tex]K.E=70.23J[/tex]
Therefore kinetic energy K.E after collision is given as
[tex]K.E=70.23J[/tex]
Help please ASAP will give brainliest
Answer:
42.64
Explanation:
2x=2
7x=5
12x=1.4
17.5x=21.5
Which diagram shows magnets that will attract each other? 2 bar magnets side by side with their long axes vertical, both red S on top and blue N on bottom. 2 bar magnets top to bottom with their long axes vertical, the top one with red S on top and blue N on bottom and the bottom magnet with blue N on top and red S on bottom. 2 bar magnets top to bottom with their long axes vertical, the top one with blue N on top and red S on bottom and the bottom magnet with red S on top and blue N on bottom. 2 bar magnets top to bottom with their long axes vertical, the top one with red S on top and blue N on bottom and the bottom magnet with red S on top and blue N on bottom.
2 bar magnets top to bottom with their long axes vertical, the top one with red S on top and blue N on bottom and the bottom magnet with red S on top and blue N on bottom. this diagram shows magnets that will attract each other. Hence option D is correct.
What is Magnet ?A permanent magnet is an item constructed of magnetised material that generates its own persistent magnetic field. A refrigerator magnet, for example, is commonly used to hold notes on a refrigerator door. Ferromagnetic (or ferrimagnetic) materials are those that can be magnetised and are strongly attracted to a magnet. These include the elements iron, nickel, and cobalt, as well as their alloys, some rare-earth metal alloys, and naturally occurring minerals such as lodestone. Although ferromagnetic (and ferrimagnetic) materials are the only ones that are strongly attracted to a magnet and are widely thought to be magnetic, all other substances respond weakly to a magnetic field via one of many different forms of magnetism.
Hence option D is correct.
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help Plz, these questions are super confusing .
Answer:
I don't know what the question is???????????????????????????????????????????????
A muon is a type of subatomic particle. If a muon is at rest in the laboratory, it will decay into an electron after about 2 microseconds. Suppose an observer watches a muon travel through the atmosphere at 90% of the speed of light. How does the lifetime of the moving muon compare to the laboratory muon for an observer at rest with respect to the lab
Answer:
[tex]\frac{t}{t_p}[/tex] = 2.29
Explanation:
For this exercise as the muon goes at speeds close to the speed of light we must use relativists
t =[tex]\frac{t_p}{\sqrt{1- (\frac{v}{c})^2 } }[/tex]
The proper time is the decay time in the reference frame where the muon is fixed ( laboratory), t_p = 2 10⁻⁶ s and the relation
v / c = 0.90
let's calculate
t = [tex]\frac{2 \ 10^{-6} }{\sqrt{1 \ - \ 0.9^2 } }[/tex]2 10-6 / Ra (1 - 0.9²)
t = 4.59 10⁻⁶ s
the ralation is
[tex]\frac{t}{t_p} = \frac{4.59 \ 10^{-6}}{ 2 \ 10^{-6}}\\[/tex]
[tex]\frac{t}{t_p}[/tex] = 2.29
A ball is thrown downward from the top of a building with an initial speed of 25 m/s.
It strikes the ground after 2.0 s. How high is the building?
20 m
30 m
50 m
70 m
Answer:
h = 69.6 m
Explanation:
Data:
Vo = 25 m/st = 2.0 sg = 9.8 m/s²h = ?Formula:
[tex]\boxed{\bold{h=V_{0}*t+\frac{g*(t)^{2}}{2}}}[/tex]Replace and solve:
[tex]\boxed{\bold{h=25\frac{m}{s}*2.0\ s+\frac{9.8\frac{m}{s^{2}}*(2.0\ s)^{2}}{2}}}[/tex][tex]\boxed{\bold{h=50\frac{m}{s^{2}}+\frac{9.8\frac{m}{s^{2}}*4\ s^{2}}{2}}}[/tex][tex]\boxed{\bold{h=50\ m+\frac{39.2\ m}{2}}}[/tex][tex]\boxed{\bold{h=50\ m+19.6\ m}}[/tex][tex]\boxed{\boxed{\bold{h=69.6\ m}}}[/tex]The building has a height of 69.6 meters.
Greetings.
1. Light moving through air is incident on a piece of crown glass (1.61) Jt an angle of 45. What is the angle of refraction?
A spring with a spring constant of 25.0N/m is stretched 4.50m. What is the force that the spring would apply?
Explanation:
[tex]from \: hookes \: law : \\ force = k \bold{.}e \\ = 25.0 \times 4.50 \\ = 112.5 \: N[/tex]
If mass is a measure of inertia of a body at rest, then momentum is a measure of inertia of a body _____
Answer:
Momentum is a measure of inertia in motion. Momentum is equal to mass multiplied by velocity. A 2250 kg pickup has a velocity of 25 m/s east.
Explanation:
Brainliest please?
.Come here G.I.R.L.S.
otd-vbut-uao
Answer:
Weird
Explanation:
Tara kain tayo sardinas lang ulam
Bobby Joe is having a fit and throws his backpack up in the air with an initial velocity of 26.2 m/s. Determine the height it will rise to before coming down and hitting Bobby Joe up the head.
A)2m
B)15m
C)25m
D)35m
Answer:
D) 35m"Explanation:
(and any subsequent words) was ignored because we limit queries to 32 words.what do electrons and holes make when they are moving
Answer:
Holes are formed when electrons in atoms move out of the valence band (the outermost shell of the atom that is completely filled with electrons) into the conduction band. (the area in an atom where electrons can escape easily) which happens everywhere in a semiconductor. When an electron and a hole interact and recombine the energy is not transferred into heat energy or thermal vibrations. instead the energy is transferred into an electron within the conduction band which is then promoted to an energy higher in condition band.
Explanation:
So considering that information, electrons and holes make a semiconductor when moving.
The Sun is a star that Earth and the other planets revolve around. The Sun has a large gravitational pull. The gravitational attraction of the Sun contributes most to which of the following?
A) Motion of the planets
B) Magnetic field of the planets
C) Mass and density of the planets
D) Atmosphere of the planets
Answer:
A
Explanation:
The sun is an emits energy in the form of light and heat.
The planets absorb this energy which helps keep them in motion. The closer they are to the sun, the more energy, the more speed and less the time it takes a planet to orbit the sun.
The gravitational pull of the Sun contributes motion of the planets because here the gravitational pull of the sun is balanced by the centrifugal force produced by the revolution of planets. The correct option Is A.
What is centrifugal force?Centrifugal force is the pseudo-force that occurs only in the rotating frame of reference (non-inertial frame). it is directed away from the center. Its magnitude is,
F=[tex]\frac{mv^{2} }{r}[/tex]
where m= mass of the body in kg.
v= velocity f the body in m/s.
r = radius in m.
The star sun has a gravitational pull that is about 274 m/s² which is greater than the other planets. Due to this pull the planets tend to pull toward the sun but it does not happen because the pull force is balanced by the centrifugal force that is produced by the revolution of the planets around the sun.
Hence The Sun's gravitational pull contributes to the motion of the planets.
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