Answer:
λ = 4.1638 10⁻⁷ m
Explanation:
The photoelectric effect was explained by Einstein assuming that the radiation acts like particles and the equation that describes the process is
K = h f -Ф
where K is the kinetic energy of the emitted electrons, hf the energy of the photons according to Planck's equation and Ф the work function of the material
In this case they give us the kinetic energy of the electrons
K = 0.7 eV
The sodium work function is tabulated Ф = 2.28 eV
Let's find the frequency of the photons
f = (K + Ф) / h
Planck's constant is
h = 6.626 10⁻³⁴ J s (1 eV / 1.6 10⁻¹⁹ J) = 4.136 10⁻¹⁵ eV s
f = (0.7 + 2.28) / 4.136 10⁻¹⁵
f = 7.2050 10¹⁴ Hz
let's find the wavelength using the relationship between speed and frequency and wavelength
c = λ f
λ = c / f
λ = 3 10⁸ / 7.205 10¹⁴
λ = 4.1638 10⁻⁷ m
A photocell is based upon the photoelectric effect. A light beam illuminates a metallic plate, and under certain conditions electrons are ejected from the metal. In order to measure the maximum kinetic energy of the electrons, another plate is kept at a negative enough potential that the emitted electrons are slowed down and stopped.
Explain how the particle-like aspect of light can explain the following:
(i) the absence of delay in the observation of current,
(ii) the existence of a cut-off frequency which is independent of the intensity of light,
(iii) the fact that the maximum kinetic energy of the electrons only depends on the frequency, not the intensity.
Answer:
i) photons, they collide with the electrons
ii)when the energy of the photons is less than the work function there is no way to get out electrons
iii) he energy depends on the frequency in this Planck postulate
Explanation:
This exercise the photo cell is used for the photoelectric effect, this effect was explained by Einstein
i) Where the light is supposed to act as a particular, therefore, it is called photons, they collide with the electrons and they can tear off the metal, with a collision it is very fast there is no measurable wait in the process.
ii) since we have a shock process, the equation must be fulfilled
K = h f - Ф
where E = h f is the energy postulated by Plank and Ф the work function of the metal, therefore when the energy of the photons is less than the work function there is no way to get out electrons, which determines a threshold energy in the process
iii) From the same previous equation, the energy depends on the frequency in this Planck postulate, and not on the intensity squared as accepted in classical mechanics.
Which describes the correct procedure when converting a number from scientific notation to standard notation if the
power of 10 is -107
Answer:
When we have a number in scientific notation like:
Ax10^n.
If n is positive, we need to add n zeros to the right of the value of A (before the decimal point)
Now, if n is negative, we need to add the decimal point n times to the left.
When we do not have any more digits in A to move the decimal point, we start to add zeros.
So for example, if we have:
7.42x10^-5
we move the decimal point 5 times to the left.
7.42x10^-5 = 0.742x10^-4 = 0.0742x10^-3 = 0.00742x10^-2
= 0.000742x10^-1 = 0.0000742.
So if we have n = -107
We move the decimal point to the left until we run out of digits in the number A, after that point, we start adding zeros in between the digits of A and the decimal point, until the number of times we moved the decimal point plus the number of zeros that we added is equal to 107.
a supertanker traveling at 7.2 m/s decelerates to a halt in 12 min. Calculate the magnitud of its average decelaration in meters per second squared
Explanation:
Acceleration is change in velocity over change in time.
a = Δv / Δt
a = (0 m/s − 7.2 m/s) / (12 min × 60 s/min)
a = -0.01 m/s²
Now you try! Draw the arrows to represent the motion described, then calculate the distance
and displacement for the object.
A car drives 12 meters North and 15 meters South What is the car's distance and
displacement
Distance = 27m
Displacement = 3 metres South
Explanation:
Distance is a scalar quantity and it represents the length of the path taken by a body.
Displacement is a vector quantity and it represents the distance between the start and end points of a body.
Now to the question:
The car drives 12 metres North i.e
North (+ve)
∧
|
| 12m
|
|
The car then drives 15 metres South i.e
|
|
|
| 15m
|
∨
South (-ve)
(a) The car's distance d, is just the total distance covered to drive North and then South. i.e
d = 12m + 15m = 27m
(b) The car's displacement D, however takes into respect, the direction of the car as it drives to and fro.
Let North be taken as positive direction
Let South be taken as negative direction.
This means that;
12 m North = +12 m
15 m South = -15m
Therefore;
D = +12 - 15
D = -3m
Since the displacement is negative, then it means that the direction of the total displacement is South.
Therefore, the displacement is 3 metres South
PS: The arrow diagram has also been attached to this response
If we ignore air resistance, a falling body will fall 16t2 feet in t seconds. What is the average velocity between t
Answer:
262.4 m/s
Explanation:
The complete question is
If we ignore air resistance, a falling body will fall 16t^2 feet in t seconds. What is the average velocity between t=8 and t=8.4? Round your answer to two decimal places if necessary.
The distance fallen s = 16t^2
The velocity v = [tex]\frac{ds}{dt}[/tex] = 32t
If we substitute the values of t into the velocity v, we'll have
at t = 8 s, V1 = 32 x 8 = 256 m/s
at t = 8.4 s, V2 = 32 x 8.4 = 268.8 m/s
Average velocity = (V2 - V1)/2 = (268.8 + 256)/2 = 262.4 m/s
How do you recognise a chemical
Vittorio needs to clean the dusty mirror hanging on the wall beforehe can use it, but he would like to clean as little of the mirroras possible.
Vittorio would like to be able to see the logo on his shirt.Draw the incident and reflected raysshowing the light from the logo reflecting off the mirror into hiseyes. The rays should meet at the point on the mirror that needscleaning.
Answer:
The drawing is attached below.
Explanation:
According to the drawing, we can see that the point "0" marked on the mirror, is the point that allows the formation of an angle between Vittorio's eyes and the place where his shirt logo is. In summary, the point on the mirror that needs to be cleaned, so that Vittorio can see only the logo of his shirt, is the point that represents equal vertical distances between Vittorio's eyes and the shirt's logo, since these distances present the same angle.
A box with the mass of 74 kg is sitting on the ground and the bottom of the box measures 90 cm by 60 cm. What is the pressure exerted by the box on the ground?
Answer: 112.5
Explanation:
divide the multiply
A resistor and an inductor are connected in series to a battery. The time constant for the circuit represents the time required for the current to reach:_______.
A.100% of the maximum current.
B. 75% of the maximum current.
C. 37% of the maximum current.
D. 25% of the maximum current.
E. 63% of the maximum current.
Optical tweezers use light from a laser to move single atoms and molecules around. Suppose the intensity of light from the tweezers is 1000 W/m2, the same as the intensity of sunlight at the surface of the Earth.
Required:
a. What is the pressure on an atom if light from the tweezers is totally absorbed? ?
b. If this pressure were exerted on a tritium atom, what would be its acceleration?
Answer:
Explanation:
a )
If it is totally absorbed pressure is calculated as follows .
Pressure = I / c where I is intensity of light falling .
= 1000 / 3 x 10⁸
= 3.33 x 10⁻⁶ N / m²
b ) weight of tritium atom
= 3 x 1.67 x 10⁻²⁷ kg
acceleration = force / mass
= 3.33x 10⁻⁶ / 3 x 1.67 x 10⁻²⁷
= .6646 x 10²¹ m /s²
= 66.46 x 10¹⁹ m / s²
A runner with a mass of 70 kg accelerates from 0 m/s to 8 m/s in 9 s. Find the magnitude of the net force (in newtons) on the runner using the alternate form of Newton's second law. Round your answer to the nearest whole number.
Explanation:
F = ma
F = m Δv / Δt
F = (70 kg) (8 m/s − 0 m/s) / 9 s
F ≈ 62 N
A thin, light wire 75.1 cm long having a circular cross section 0.555 mm in diameter has a 25.4 kg weight attached to it, causing it to stretch by 1.10 mm.
A) what is the stress of the wire.
B) what is the strain in the wire.
C) find the Young Modulus for the material of the wire.
Answer:
(a) 3.23×10⁸ N/m²
(b) 1.46×10⁻³
(c) 2.21×10¹¹ N/m²
Explanation:
(a) Stress = Force/Area.
Stress = F/A................ Equation 1
But,
F = mg................. Equation 2
Where m = mass, and g = acceleration due to gravity
A = πd²/4................. Equation 3
d = diameter of the circular cross section.
Substitute equation 2 and equation 3 into equation 1
Stress = 4mg/πd²............. Equation 4
Given: m = 25.4 kg, d = 0.555 mm = 0.000555 m
Constant: g = 9.8 m/s², π = 3.142
Substitute these values into equation 4
Stress = 4(25.4)(9.8)/(3.142×0.00555²)
Stress = 995.68/(3.08×10⁻⁶)
Stress = 3.23×10⁸ N/m²
(b)
Strain = ΔL/L.............. Equation 5
Where ΔL = extension, L = Length.
Given: ΔL = 1.1 mm = 0.0011 m, L = 75.1 cm = 0.751 m
Substitute into equation 5
Strain = 0.0011/0.751
Strain = 1.46×10⁻³.
(c)
Young modulus = Stress/Strain
Young modulus = 3.23×10⁸/ 1.46×10⁻³
Young modulus = 2.21×10¹¹ N/m²
PLEASE HELP WITH PHYSICS HOMEWORK ASAP
Your bedroom has a rectangular shape and you want to measure its size. You use a tape that is precise to 0.001 m and find that the shortest wall in the room is 3.547 m long. The tape, however, is too short to measure the length of the second wall, so you use a second tape, which is longer but only precise to 0.01 m. You measure the second wall to be 4.79 m long. Which of the following numbers is the most precise estimate that you can obtain from your measurements for the area of your bedroom?
a) 30 m^2.
b) 31.4 m^2.
c) 31.37 m^2.
d) 31.371 m^2.
Your bedroom has a rectangular shape, and you want to measure its area. You use a tape that is precise to 0.001 and find that the shortest wall in the room is 3.547 long. The tape, however, is too short to measure the length of the second wall, so you use a second tape, which is longer but only precise to 0.01 . You measure the second wall to be 4.79 long. Which of the following numbers is the most precise estimate that you can obtain from your measurements for the area of your bedroom?
b)If your bedroom has a circular shape, and its diameter measured 6.32 , which of the following numbers would be the most precise value for its area?
a)30 m^2
b) 31.4 m^2
c)31.37 m^2
d)31.371 m^2
Answer:
Part A
[tex]A = 16.99 \ m^2[/tex]
Part B
[tex]A_r =31.37 \ m^2[/tex]
Explanation:
From the question we are told that
The shortest wall is [tex]x = 3.547 \ m[/tex]
The length of the second wall is [tex]y = 4.79 \ m[/tex]
Generally the area is mathematically evaluated as
[tex]A = x * y[/tex]
=> [tex]A = 3.547 * 4.79[/tex]
=> [tex]A = 16.99 \ m^2[/tex]
Given that the diameter is d = 6.32
Then the area is
[tex]A_r = \pi \frac{d^2}{4}[/tex]
[tex]A_r =3.142 * \frac{6.32^2}{4}[/tex]
[tex]A_r =31.37 \ m^2[/tex]
At what frequency should a 200-turn, flat coil of cross sectional area of 300 cm2 be rotated in a uniform 30-mT magnetic field to have a maximum value of the induced emf equal to 8.0 V
Answer:
The frequency of the coil is 7.07 Hz
Explanation:
Given;
number of turn of the coil, N = 200 turn
area of the coil, A = 300 cm² = 0.03 m²
magnitude of magnetic field, B = 30 mT = 0.03 T
maximum value of induced emf, E = 8 V
The maximum induced emf in the coil is given by;
E = NBAω
E = NBA(2πf)
[tex]f = \frac{E_{max}}{2\pi*NBA}[/tex]
where;
f is the frequency of the coil
[tex]f = \frac{E_{max}}{2\pi*NBA}\\\\f = \frac{8}{2\pi(200)(0.03)(0.03)} \\\\f = 7.07 \ Hz[/tex]
Therefore, the frequency of the coil is 7.07 Hz
With what minimum speed must you toss a 130 g ball straight up to just touch the 14-m-high roof of the gymnasium if you release the ball 1.1 m above the ground
THIS IS THE COMPLETE QUESTION BELOW
With what minimum speed must you toss a 130 g ball straight up to just touch the 14-m-high roof of the gymnasium if you release the ball 1.1 m above the ground
And what speed does the ball hit the ground? Solve this problem using energy.
Answer
a)minimum speed must you toss a 130 g is 15.9090m/s
b)speed the ball hit the ground is 16.57m/s
Explanation:
a)We know that For any closed/isolated system, the total energy is CONSERVED.
K.E. lost by the ball=The change in P.E of the ball at 1.1m above the ground as well as the P.E. of the ball at 14 m-high roof
This statement can be expressed as the expression below from K.E and P.E energy formula
P.E. = mgh
K.E. = (1/2)mv^2
Therefore,
(mgh1 - mgh2)=(1/2)mv^2
Where h2=the ball height above the ground=1.1m
h1=ball height at roof of the gymnasium= 14m
Then if we substitute we have
[(10) x (0.14) x (9.81)] - [(1.1) x (0.14) x (9.81)] = (1/2)(0.14)(v^2)
16.45137=0.065V^2
V=15.9090m/s
minimum speed must you toss a 130 g is 15.9090m/s
b)To calculate the speed the ball hit the ground?
This is the highest point (14m-high roof),and the type of the energy the ball possesses is Po.tential energy only.
At the lowest point (ground), the energy the ball possesses is K.E. only.
P.E at 10m-high roof = K.E. at ground.
(14) x (0.13) x (9.81) = (1/2) x (0.13) x v^2
17.8542= 0.065V^2
V= 16.57
Therefore,And speed the ball hit the ground is 16.57m/s
A gas is compressed by an adiabatic process that decreases its volume by a factor of 2.
In this process, the pressure
In this process, the pressure
a) increases by a factor of more than 2.
b) increases by a factor of 2.
c) does not change.
d) increases by a factor of less than 2.
Answer
OPTION A is correct
a)increases by a factor of more than 2.
Explanation:
adiabatic process is a process that takes place without the transfer of heat or mass between a thermodynamic system and its surroundings.
It is a process in which no heat transfer takes place. It does not denote that the temperature is constant.
Then from an adiabatic system,
we know that
PV= constant
PV^γ= constant
γ=ratio of specific heat for the gas
Where P= pressure of the system
V= volume of the system
We can say P= 1/(V^γ)
Where γ >1
Which means the pressure is inversely proportional to the volume raise to power of gamma sign and whenever the pressure increases the volume decreases with V^γ.
The question says the volume is decreased by factor of two then V^γ will also decreased by factor of 2.
That means (2^γ) > 2
Since our γ > 1 Therefore, the pressure increases by a factor of more than 2.
Answer:
a) increases by a factor of more than 2.
Explanation:
In an adiabatic process,
[tex]PV^{Y} = constant[/tex]
we can say that the volume is inverse to the pressure as
[tex]V^{Y}[/tex]∝ [tex]\frac{1}{P}[/tex]
where
[tex]P[/tex] is the pressure
[tex]V[/tex] is the volume
[tex]Y[/tex] is the adiabatic index, and it is always greater than 1
If volume V is decreased by a factor of 2, then it is actually decreased by a factor of [tex]2^{Y}[/tex] in proportion to the pressure, and since [tex]Y[/tex] is always greater than 1, it is actually decreased by a factor greater than 2 in proportion to the pressure.
This means that the pressure will also increase by a factor greater than 2.
When a cube is inscribed in a sphere of radius r, the length Lof a side of the cube is . If a positive point charge Qis placed at the center of the spherical surface, the ratio of the electric flux sphereat the spherical surface to the flux cubeat the surface of the cube is(sphere / cube)
Answer:
Ф_cube /Ф_sphere = 3 /π
Explanation:
The electrical flow is
Ф = E A
where E is the electric field and A is the surface area
Let's shut down the electric field with Gauss's law
Фi = ∫ E .dA = [tex]q_{int}[/tex] / ε₀
the Gaussian surface is a sphere so its area is
A = 4 π r²
the charge inside is
q_{int} = Q
we substitute
E 4π r² = Q /ε₀
E = 1 / 4πε₀ Q / r²
To calculate the flow on the two surfaces
* Sphere
Ф = E A
Ф = 1 / 4πε₀ Q / r² (4π r²)
Ф_sphere = Q /ε₀
* Cube
Let's find the side value of the cube inscribed inside the sphere.
In this case the radius of the sphere is half the diagonal of the cube
r = d / 2
We look for the diagonal with the Pythagorean theorem
d² = L² + L² = 2 L²
d = √2 L
we substitute
r = √2 / 2 L
r = L / √2
L = √2 r
now we can calculate the area of the cube that has 6 faces
A = 6 L²
A = 6 (√2 r)²
A = 12 r²
the flow is
Ф = E A
Ф = 1 / 4πε₀ Q/r² (12r²)
Ф_cubo = 3 /πε₀ Q
the relationship of these two flows is
Ф_cube /Ф_sphere = 3 /π
A woman rides a carnival Ferris wheel at radius 16 m, completing 4.5 turns about its horizontal axis every minute. What are (a) the period of the motion, and the magnitude of her centripetal acceleration at (b) the highest point and (c) the lowest point
Answer:
a)13.33s
b)at highest point, the centripetal acceleration has its direction at downward path towards the center of the circular path, and the radius vector has its direction upward. Then acceleration=3.555m/s^2
c)c)at lowest point the centripetal acceleration has its direction upward towards the center of the circular path, and the radius vector has its direction downward Then acceleration=3.555m/s^2
Explanation
a)number of turns= 4.5
radius= 16m
We know that the period is the time taken by the wheel to complete one turn which can be calculated using below expresion
T= t/n
Where T= period of motion
t= Time taken by the wheel to finish n turns where our n= 4.5
T= (1×60)/4.5= 13.33s
Hence the period is 13.33s
Then the speed of the woman v= 2πr/T
v= (2×π×16)/13.33
v=7.5417m/s
b)at highest point, the centripetal acceleration has its direction at downward path towards the center of the circular path, and the radius vector has its direction upward.
a= v^2/r
Where r= radius
v= speed of the woman= 7.5417m/s
a=(7.5417m/s)^2/16
a=3.555m/s^2
The centripetal acceleration and radius vector are in opposite direction
c)at lowest point the centripetal acceleration has its direction upward towards the center of the circular path, and the radius vector has its direction downward
The magnitude of the acceleration is calculated below
a= v^2/r
Where r= radius
v= speed of the woman= 7.5417m/s
a=(7.5417m/s)^2/16
a=3.555m/s^2
in a 200 m swimming competition,a swimmer took 12.3s to complete the first lap,12.5 for the second lap,12.7 for the third lap and 12.6 for the fourth lap.Each lap is 50 m long.Find the average speed and average velocity of the swimmer
Explanation:
Distance is the length of the path. Displacement is the difference between the final position and the initial position.
Speed = distance / time
= (50 m + 50 m + 50 m + 50 m) / (12.3 s + 12.5 s + 12.7 s + 12.6 s)
= (200 m) / (50.1 s)
= 3.99 m/s
Velocity = displacement / time
= (50 m − 50 m + 50 m − 50 m) / (12.3 s + 12.5 s + 12.7 s + 12.6 s)
= (0 m) / (50.1 s)
= 0 m/s
A voltmeter and an ammeter are used to respectively monitor the voltage across and the current through a resistor connected to an AC source. If the resistor has a value of 11.5 Ω and the ammeter reads 7.24 A, determine the following.
(a) the rms voltage (in V) across the resistor
(b) the peak voltage (in V) of the source
(c) the maximum current (in A) in the resistor
(d) the average power (in W) delivered to the resistor
Answer:
a) 85.1 V
b)120.4 V
c) 10.24 A
d) 602.8 W
Explanation:
The reading of the ammeter is the root mean square value of current.
a) Vrms= Irms R
Irms= 7.24 A
R= 11.5 Ω
Vrms= 7.4A × 11.5Ω
Vrms= 85.1 V
b)
Peak value of voltage (Vo)= Vrms/0.707
Vo=85.1/0.707
Vo=120.4 V
c)
Peak current= Irms/0.707
Io= 7.24/0.707
Io= 10.24 A
d) average power= Irms^2 × R
Power= (7.24)^2 ×11.5
Power= 602.8 W
Represent a vector of 100 N in North-East direction
Answer:
N 100N E
Explanation:
Check image uploaded for the solution
What happens when two waves meet while they travel through the same medium
Wave Interference or Interference of wave
If, while standing on the bank of a stream, you wished to spear a fish swimming in the water out in front of you, would you aim above, below, or directly at the observed fish to make a direct hit? If you decided to instead zap the fish with a laser, would you aim above, below, or directly at the observed fish? Defend your answers.
Answer:
a) below the observed position
b) directly at the observed position
Explanation:
If I'm standing on the bank of a stream, and I wish to spear a fish swimming in the water out in front of me, I would aim below the observed fish to make a direct hit. This is because the phenomenon of refraction of light in water causes the light coming from the fish is refract away from the normal as it passes into the air and into my eyes.
If I'm to zap the fish with a taser, I would aim directly at the observed fish because the laser (a form of concentrated light waves) will refract into the water, taking the same path the light from the fish took to get to my eyes.
If someone were monitoring your vital signs (like your heart rate, oxygen content in your blood, blood pressure, etc.) every hour in a hospital, you would
likely want them to be both accurate and precise in their measurements. Make an argument for why what you think is more important, accuracy or
precision?
Answer:
Accuracy
Explanation:
I think accuracy is more important. When it comes to vital organs in the body, the exactness of getting the measurement is paramount. Accuracy deals with getting very close, almost exact you may say, to a known standard. Precision on the other hand, deals with how easy a measurement can be retaken, reproduced or remade, irrespective of how far or close they are from the accepted norm.
From this, we can agree that precision neglects the most important factor, closeness or say, exactness. Precision isn't bothered by it. And while that can be excused in a few instances, it certainly can not be permitted when it comes to life, or organs of the body
Joe rides south on his bicycle in a straight line for 16 min with an average speed of 11.6 km/h , how far has he ridden? Answer in units of km.
Explanation:
Distance = speed × time
d = (11.6 km/h) (16 min × 1 hr / 60 min)
d = 3.09 km
Answer: distance = 3.09 km
Explanation: Distance = speed × time
distance = (11.6 km/h) (16 min × 1 hr / 60 min)
distance = 3.09 km
HOPE THIS HELPS YOU..
PLS MARK ME IN BRAINLIESTA worker needs to know the temperature inside an oven. He takes a 2 kg iron bar out of the oven and places it in a 1 kg aluminum container partially filled with 2 kg of water. If the water temperature rises from 21 ° C to 50 ° C, what was the temperature of the oven? Neglect other heat changes.
Answer:
350°C
Explanation:
Heat gained by water and aluminum = heat lost by iron
q₁ + q₂ = -q
m₁C₁ΔT₁ + m₂C₂ΔT₂ = -mCΔT
(1 kg) (900 J/kg/°C) (50°C − 21°C) + (2 kg) (4186 J/kg/°C) (50°C − 21°C) = -(2 kg) (449 J/kg/°C) (50°C − T)
(900 J/°C) (29°C) + 2 (4186 J/°C) (29°C) = -2 (449 J/°C) (50°C − T)
26,100 J + 242,788 J = -44,900 J + 898 (J/°C) T
898 (J/°C) T = 313,788 J
T = 350°C
If the f-number of a camera lens is doubled, say from F4.0 to F8.0, that means the diameter of the lens aperture is
Answer:
The diameter is halved or reduced by a factor of 2
Explanation:
Because
f number = F/D
That is f number is inversely proportional to diameter so if it is doubled diameter is halved
An electron and a proton are each accelerated from rest through a potential difference of 100 V. Afterward, which particle has the larger de Broglie wavelength?
Explanation:
The De-Broglie wavelength in terms of potential difference is given by:
[tex]\lambda=\dfrac{h}{\sqrt{2meV} }[/tex]
Where,
h is Planck's constant
m is mass of charged particle
V is potential difference
e is the amount of charge
It means that the De-Broglie wavelength is inversely proportional to the mass.
Since, the mass of the proton is more than the mass of the electron. So, the De- Broglie wavelength of the electron is larger than proton.
What should a model of the rock cycle show as the process that changes metamorphic rock to igneous rock?
Answer:
Rock cycle describes the concept in geology that shows the changes in the rock type in the geologic time.
Many processes undergoes in the rock cycle that leads to transition of rocks, the process that changes metamorphic rock to igneous rock is melting and crystallization. The metamorphic rock melts under high pressure and temperature and which crystallizes into a completely different kind of rock, called igneous rock.
Answer:
Melting followed by cooling