A light-emitting diode (LED) connected to a 3.0 V power supply emits 440 nm blue light. The current in the LED is 11 mA , and the LED is 51 % efficient at converting electric power input into light power output. How many photons per second does the LED emit?
Answer:
3.73 * 10^16 photons/sec
Explanation:
power supply = 3.0 V
Emits 440 nm blue light
current in LED = 11 mA
efficiency of LED = 51%
Calculate the number of photons per second the LED will emit
first step : calculate the energy of the Photon
E = hc / λ
=( 6.62 * 10^-34 * 3 * 10^8 ) / 440 * 10^-9
= 0.0451 * 10^-17 J
Next :
Number of Photon =( power supply * efficiency * current ) / energy of photon
= ( 3 * 0.51 * 11 * 10^-3 ) / 0.0451 * 10^-17
= 3.73 * 10^16 photons/sec
Suppose that 2 J of work is needed to stretch a spring from its natural length of 28 cm to a length of 43 cm. (a) How much work is needed to stretch the spring from 33 cm to 35 cm
Answer:
0.035 J
Explanation:
Applying,
W = ke²/2.............. Equation 1
Where W = workdone by the stretching the spring, k = spring constant, e = extension.
make k the subject of the equation
k = 2W/e²............... Equation 2
From the question
Given: W = 2 J, e = (43-28) = 15 cm = 0.15 m
Substitute these values into equation 2
k = (2×2)/(0.15²)
k = 177.78 N/m
Hence, work need to stretch the spring from 33 cm to 35 cm
therefore,
e = 35-33 = 2 cm = 0.02 m
Substitute into equation 1
W = 177.78(0.02²)/2
W = 0.035 J
Calculate the heat energy conducted per hour through the side walls of a cylindrical steel
boiler of 1.00 m diameter and 3.0 m long if the internal and external temperatures of the
walls are 140 °C and 40 °C respectively and the thickness of the walls is 6.0 mm. (Thermal
conductivity of steel, k = 42 Wm-4°C-4)
Explanation:
heat caoacity and heat is difference
The heat energy conducted per hour through the side walls of the cylindrical steel boiler is 27708847 kJ.
What is thermal conductivity?The rate at which heat is transported by conduction through a material's unit cross-section area when a temperature gradient exits perpendicular to the area is known as thermal conductivity.
In the International System of Units (SI), thermal conductivity is measured by Wm⁻¹K⁻¹.
Diameter of the cylindrical steel boiler: d = 1.00m.
Length of the cylindrical steel boiler: l = 3.00m.
thickness of the walls is = 6.0 mm = 0.006 m
Temperature gradient is = (140-40) °C/0.006 m = 1666.67 °C/m
Thermal conductivity of steel, = 42 W/m-°C.
Hence, the heat energy conducted per hour through the side walls of the cylindrical steel boiler = 42×3600×1666.67 ×2π×0.5(0.5+3.0) Joule
= 27708847 kJ
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1. Lifting an elevator 18m takes 100kJ. If doing so takes 20s, what is the average power of the elevator during the process?
2. How much work can a 0.4 hp electric mixer do in 15 s?
Answer:
1. Power = 5000 Watts
2. Workdone = 11185.5 Joules
Explanation:
Given the following data;
1. Distance = 18 m
Energy = 100 KJ = 100,000 Joules
Time = 20 seconds
To find the average power of the elevator;
Power = energy/time
Power = 100000/20
Power = 5000 Watts
2. Power = 0.4 HP
Time = 15 seconds
Conversion:
1 horsepower = 745.7 Watts
0.4 horsepower = 0.4 * 745.7 = 298.28 Watts
To find the amount of work done by the electric mixer;
Work done = power * time
Workdone = 745.7 * 15
Workdone = 11185.5 Joules
15. A car is stationary at the top of a hill with the engine
switched off. The brakes are released and the car rolls down
the hill. At which labelled point does the car have the greatest
kinetic energy? *
A
Answer:
kinetic energy
Explanation:
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A farmhand pushes a 23 kg bale of hay 3.9 m across the floor of a barn. If she exerts a horizontal force of 91 N on the hay, how much work has she done?
Answer:
W = 354.9 J
Explanation:
Given that,
The mass of a bale of hay, m = 23 kg
The displacement, d = 3.9 m
The horizontal force exerted on the hay, F = 91 N
We need to find the work done. We know that,
We know that,
Work done, W = Fd
So,
W = 91 N × 3.9 m
W = 354.9 J
So, the required work done is 354.9 J.
A spinning satellite begins to unfold two solar panels as shown. As the
panels extend from the satellite, what is the result?
Its angular momentum of a satellite will drop even as satellite panel stretch because of the reduction in angular velocity brought on by the drag effect.
Why then do stars spin more quickly during their demise?A portion of the star's mass is blown off during the supernovae that come before the creation of black holes, taking some of the star's total angular momentum with it.The leftover material sinks into the star's core while continuing to spin rapidly.
What is the name of the spinning effect?Magnus effect: When there is relative movement between both the spinning item and the fluid, a sideways force is generated on a rotating cylindrical or spherical object immersed in the fluid (liquid or gas).In honor of the German chemist and physicist H.G.
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Two microwave signals of nearly equal wavelengths can generate a beat frequency if both are directed onto the same microwave detector. In an experiment, the beat frequency is 170MHz . One microwave generator is set to emit microwaves with a wavelength of 1.410cm.
If the second generator emits the longer wavelength, what is that wavelength?
Answer:
The wavelength of the wave is 1.419 cm.
Explanation:
wavelength emitted by the one micro wave = 1.41 cm
beat frequency = 170 M Hz
Let the frequency of the wave is f.
[tex]f=\frac{c}{\lambda }\\\\f =\frac{3\times 10^8}{0.0141}\\\\f = 2.13\times 10^{10} Hz[/tex]
Let the frequency of the other wave is f'.
[tex]f' = 2.13\times 10^{10}-170\times10^6\\\\f' = 21130\times 10^6 Hz[/tex]
The wavelength is given by
[tex]f' = 21130\times 10^6 Hz\\\lambda = \frac{3\times 10^8}{21130\times 10^6}\\\\\lambda = 0.01419 m = 1.419 cm[/tex]
The rotating loop in an AC generator is a square 18 cm on each side. It is rotated at 60.0 Hz in a uniform magnetic field of 0.3T. Calculate the approximate value of the maximum amplitude of the power delivered to the loop for a loop resistance of 12 ohm ?
Answer:
The maximum amplitude power is 1.12 W
Explanation:
Given;
length of each side of the square, L = 18 cm = 0.18 m
angular frequency, f = 60 Hz
magnetic field, B = 0.3 T
resistance of the loop, R = 12 ohm
The area of the loop, A = L² = 0.18 m x 0.18 m = 0.0324 m²
The angular speed, ω = 2πf = 2π x 60 = rad/s = 377.04 rad/s
The maximum value of emf induced;
[tex]E_{max} = NBA \omega\\\\where; \\N \ is \ number \ of \ turns\\\\E_{max} = (1) \times 0.3 \times 0.0324 \times 377.04\\\\E_{max} = 3.665 \ V[/tex]
The maximum amplitude power is calculated as;
[tex]Power = \frac{(E_{max})^2 }{R} \\\\Power = \frac{(3.665)^2}{12} \\\\Power = 1.12 \ W[/tex]
Six artificial satellites complete one circular orbit around a space station in the same amount of time. Each satellite has mass m and radius of orbit L. The satellites fire rockets that provide the force needed to maintain a circular orbit around the space station. The gravitational force is negligible.
Rank the net force acting on each satellite from their rockets. Rank from largest to smallest.
a. m=200 kg and L= 5000m
b. m=400 kg and L=2500m
c. m=100kg and L=2500m
d. m=100kg and L=10000m
e. m=800kg and L=5000m
f. m=300kg and L=7500m
Answer:
b = e > a = c = f > d
Explanation:
Since the satellites complete one circular orbit in the same amount of time, their speed is the same.
The force needed to maintain the orbit is the centripetal force given by F = mv²/L where m = mass of artificial satellite and L = radius of orbit.
So, for artificial satellite a
a. m=200 kg and L= 5000m
F = mv²/L
F = 200 kgv²/5000 m
F = 0.04v² N
So, for artificial satellite b
b. m=400 kg and L= 2500m
F = mv²/L
F = 400 kgv²/2500 m
F = 0.16v² N
So, for artificial satellite c
c. m=100 kg and L= 2500m
F = mv²/L
F = 100 kgv²/2500 m
F = 0.04v² N
So, for artificial satellite d
d. m=100 kg and L= 10000m
F = mv²/L
F = 100 kgv²/10000 m
F = 0.01v² N
So, for artificial satellite e
e. m=800 kg and L= 5000m
F = mv²/L
F = 800 kgv²/5000 m
F = 0.16v² N
So, for artificial satellite f
f. m=300 kg and L= 7500m
F = mv²/L
F = 300 kgv²/7500 m
F = 0.04v² N
So, the net force are in the order b = e > a = c = f > d
The energy wasted in using a machine is 600j. if the machine is 70% efficient. calculate the volume of water pumb by the machine through a height of 15m.
Answer:
yhgigy6ftu5cg l8vbbnnbbgtccccvhklhaywje nc 62bbnzmakbdbvfvdbf93bdldmffmfkqhdv
An object that gives off electromagnetic waves based on its temperature
demonstrates which phenomenon?
A. Emission spectra
B. Blackbody radiation
C. Quantum mechanics
D. Photoelectric effect
Answer:
B) Blackbody radiation
MARK THIS AS BRAINLIEST PLEAWESSS :)
Answer:
Black body radiation
Explanation:
Suppose the Earth were squeezed down to the size of a small mountain. The mass of the Earth would not change, just its volume and radius. If you were now standing on the surface, would the gravitational force on you be greater than, less than or the same as before the Earth was squeezed?
Explanation:
Much greater. Gravitational force depends on the mass and separation distance. Shrinking the earth means the mass remains the same while the radius gets smaller. Since gravitational force is inversely proportional to the square of the separation distance, as shown by Newton's universal gravitational law
[tex]\:\:\:F_G = G \dfrac{mM_E}{R^2}[/tex]
shrinking the radius even by a factor of 10 will cause your weight, which also happens to be the gravitational force of the earth on you, to be 100 times more.
If the mass of the Earth remains the same and only its volume and radius are decreased, then the average density of the Earth would increase significantly.
What is gravitational force?Gravity, also known as gravitational force, pulls objects with mass towards each other. We frequently consider the force of gravity from Earth.
If the Earth's mass remains constant while its volume and radius are reduced, the average density of the Earth increases significantly.
This is due to the fact that the mass has been compressed into a much smaller volume.
As a result, standing on the surface, the gravitational force on you would be greater than before the Earth was compressed to the size of a small mountain.
When the Earth is compressed, the distance between you and the center of the Earth decreases while the mass remains constant.
Thus, your gravitational force increases.
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4. You currently have TWO 9 volt batteries connected to a 82 resistor. How
much current is flowing through the circuit? *
1.125 A
5 A
72 A
2.25 A
Back
Next
Never submit passwords through Gon
Explanation:
Total voltage = 9 × 2 = 18v
Resistance = 82 Ω
Ohm's law::
V = IR
18v = 82 Ω × I
18v /82 /Ω = I
18/82 Ampere is the current
Directions: Analyze and illustrate the given problems. Show your mathematical equations.
1. How much work is done when you lift an object that weighs 180 N to a height of 12 meters?
2. A cylindrical container having a mass of 50 kg is being pushed up an inclined plane. How much work
is done on the container when it is 6 meters above the floor?
3. How much work do you do to a 16-N rock that you carry horizontally across a 4m room?
Answer:
1. 2160 J
2. 2940 J
3. 64 J
Explanation:
1. Determination of the work done.
Weight (W) = 180 N
Height (h) = 12 m
Workdone =?
Wd = W × h
Wd = 180 × 12
Wd = 2160 J
Thus, the Workdone is 2160 J
2. Determination of the work done.
Mass (m) = 50 Kg
Height (h) = 6 m
Acceleration due to gravity (g) = 9.8 m/s²
Workdone =?
Wd = mgh
Wd = 50 × 9.8 × 6
Wd = 2940 J
Thus, the Workdone is 2940 J
3. Determination of the work done.
Force (F) = 16 N
Distance (d) = 4 m
Workdone =?
Wd = F × d
Wd = 16 × 4
Wd = 64 J
Thus, the Workdone is 64 J
15. Muous produced by snails help them move along the ground How does the mucus help maits
move?
A Mucus is cold
C. Mucus reduces friction
B. Mucus leaves a trail D. Mucus makes the snail lighter
16. Which of the following statements does NOT tell about the effects of pravitational force
on objects?
A. The more distant the body from the earth, the lesser is the gravitational force of attraction
B. Gravitational force pushes the objects upward
C. Gravitational force is greater when the objects are closer together
D. The farther you are from earth, the lesser your weight
17. Why is it difficult for us to go up in a mountain than go down?
A We are moving against gravity
B. We are pulled by the wind
C. We are moving towards gravity
D. None of the above
18. Which of these will have the strongest gravitational pull on Earth'?
A a baby
C. a drinking glass
B. a half sack of nice
D. an elephant
19. Without air resistance, all objects fall at the same rate.
D. Neither True or False
C Maybe
B. False
20. The gravity between two objects increases as the distance between them
D stabilizes
C neutralizes
B. increases
A. decreases
A True
Answer:
15.C Mucus reduces friction
20 points, im begging for help‼️
How much capacitance is needed to
store 0.00100 J of energy when the
charge on the capacitor is
4.86 x 10-5 C?
[?] x 10?!F
Answer:
Capacitance= 1.18×10^-6
Answer: 1.18*10^-6
Explanation:
A professional quarterback throws a 0.40 kg football. what is the force of weight?
Answer:
3.92N
Explanation:
Force= mass×accelerarion due gravity
But mass= 0.40kg
acceleration due to gravity = 9.8 m/s^2
Force = 0.40×9.8
Force=3.92N
____can be used to transmit information
A heat
B patterns
c senses
D digital
Answer:
D. digital
Explanation:
Digital signals are transmitted through electromagnetic waves.
I'm not sure
A rectangular field is of length 42 cm and breadth 25 m. Find the area of the field in SI unit. EXPLAIN STEP BY STEP
Answer:
the area of the rectangular field is 10.5 m²
Explanation:
Given;
length of the rectangular field, L = 42 cm = 0.42 m
breadth of the rectangular field, b = 25 m
The area of the rectangular field is calculated as follows;
Area = Length x breadth
Area = 0.42 m x 25 m
Area = 10.5 m²
Therefore, the area of the rectangular field is 10.5 m²
1. Calculate the density of a 5.00 g marble which, when placed in a
graduated cylinder containing 60 milliliters of water, raised the volume of
the water to 68 milliliters.
2. An elevator with a mass of 1000kg is lifted 20 meters. How much work
was done on the elevator?
3. Calculate the potential energy of a 12 kg cat at the top of a 42 meter-
high hill.
4. Calculate the kinetic energy in joules of a 1500 kg car that is moving at a
speed of 10 m/s.
Answer:
1. 0.625 g/mL
2. 2×10⁵ J
3. 5040 J
4. 75000 J
Explanation:
1. Determination of the density.
We'll begin by calculating the volume of the marble. This can be obtained as follow:
Volume of water = 60 mL
Volume of water + Marble = 68 mL
Volume of marble =?
Volume of marble = (Volume of water + Marble) – (Volume of water)
Volume of marble = 68 – 60
Volume of marble = 8 mL
Finally, we shall determine the density of the marble. This can be obtained as follow:
Mass of marble = 5 g
Volume of marble = 8 mL
Density of marble =?
Density = mass / volume
Density of marble = 5 / 8
Density of marble = 0.625 g/mL
2. Determination of the work done.
Mass (m) = 1000 Kg
Height (h) = 20 m
Acceleration due to gravity (g) = 10 m/s²
Workdone (Wd) =?
The work done can be obtained as follow:
Wd = mgh
Wd = 1000 × 10 × 20
Wd= 2×10⁵ J
3. Determination of the potential energy.
Mass (m) = 12 Kg
Height (h) = 42 m
Acceleration due to gravity (g) = 10 m/s²
Potential energy (PE) =?
The potential energy can be obtained as follow:
PE = mgh
PE = 12 × 10 × 42
PE = 5040 J
4. Determination of the kinetic energy.
Mass (m) = 1500 Kg
Velocity (v) = 10 m/s
Kinetic energy (KE) =?
The kinetic energy can be obtained as follow:
KE = ½mv²
KE = ½ × 1500 × 10²
KE = 750 × 100
KE = 75000 J
In June 1985, a laser beam was sent out from the Air Force Optical Station on Maui and reflected back from the shuttle Discovery as it passed by 354 km overhead. The diameter of the central maximum of the beam at the shuttle position was 500 nm. What is the effective diameter of the circular laser aperture at the Maui ground station
This question is incomplete, the complete question is;
In June 1985, a laser beam was sent out from the Air Force Optical Station on Maui and reflected back from the shuttle Discovery as it passed by 354 km overhead. The diameter of the central maximum of the beam at the shuttle position was said to be 9.1 m, and the beam wavelength was 500 nm.
What is the effective diameter of the circular laser aperture at the Maui ground station
Answer:
the effective diameter of the circular laser aperture at the Maui ground station is 4.747 cm
Explanation:
Given the data in the question;
Separation between observer and point L = 354 km = 354000 m
Linear separation D = 9.1 m
wavelength λ = 500 nm = 500 × 10⁻⁹ m
Now, for small angles;
θ = D / L
θ = 9.1 m / 354000 m
θ = 2.57 × 10⁻⁵ rad
For a circular aperture;
sinθ = ( 1.22 × λ ) / d
for small angles;
θ = ( 1.22 × λ ) / d
so
θ = 2 × θ
θ = 2 × [( 1.22 × λ ) / d]
we substitute
2.57 × 10⁻⁵ = 2 × [( 1.22 × 500 × 10⁻⁹ ) / d]
2.57 × 10⁻⁵ = 0.00000122 / d
d = 0.00000122 / 2.57 × 10⁻⁵
d = 0.04747 m
d = ( 0.04747 × 100 )m
d = 4.747 cm
Therefore, the effective diameter of the circular laser aperture at the Maui ground station is 4.747 cm
A motor has an output of 1000 watts. When the motor is working a full capacity, how much time will it require to lift a 50 Newton weight 100 meters?
The time required to lift the weight is 5 seconds.
What is time?Time is the measure of past or present events or occurrences. The S.I unit of time is seconds (s).
To calculate the time required to lift the weight, we use the formula below.
Formula:
P = Fd/t.................. Equation 1Where:
P = PowerF = Weightd = distance.t = timemake t the subject of the equation.
t = Fd/P................ Equation 2From the question,
Given:
F = 50 Nd = 100 mP = 1000 WSubstitute these values into equation 2
t = (50×100)/1000t = 5 seconds.Hence, The time required to lift the weight is 5 seconds.
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PLEASE HELP ME WITH THIS ONE QUESTION
What is the rest energy of a proton? (c = 2.9979 x 10^9 m/s, mp = 1.6726 x 10^-27)
A) 8.18 x 10^-14 J
B) 2.73 x 10^-22 J
C) 1.5053 x 10^-10 J
D) 1.5032 x 10^-10 J
Answer:
D) 1.5032 x 10^-10 J
Explanation:
The rest energy of a proton, E₀, follows the equation:
E₀ = mp*rate²
Where mass of proton, mp = 1.6726 x 10^-27kg
rate = 2.9979 x 10^8 m/s (2.9979 x 10^9 m/s is not the speed light)
E₀ = 1.6726 x 10^-27kg * (2.9979 x 10^8 m/s)²
E₀ =1.5032 x 10^-10 J
Right answer is:
D) 1.5032 x 10^-10 JSuppose 4 J of work are needed to stretch a spring 14 cm from its natural position. How much work is needed to stretch it 20 cm from its natural position
Answer:
8.16 J
Explanation:
Applying,
W = ke²/2................. Equation 1
Where W = work done in stretching the spring, k = spring constant, e = extension
make k the subject of the equation
k = 2W/e²................ Equation 2
From the question,
Given: W = 4 J, e = 14 cm = 0.14 m
Substitute these values into equation 2
k = 2(4)/0.14²
k = 8/0.0196
k = 408.16 N/m
If stretchd 20 cm from its natural length,
Therefore,
e = 20 cm = 0.2 m
W = 408.16(0.2²)/2
W = 8.16 J
Definition of Xenophobia
Answer:
dislike of or prejudice against people from other countries.
Explanation:
Answer: dislike of or prejudice against people from other countries.
Explanation:
the two factors that affect the amount of heat
Answer:
The two important factors that affect heat energy are specific heat and temperature. Specific heat is a heat-constant of a material per unit mass per degree of temperature change (in units of energy per mass and temperature), like Joules/Kg-°C .
Thank you.....
Have a good day.....
An unstretched ideal spring hangs vertically from a fixed support. A 0.4 kg object is then attached to the lower end of the spring. The object is pulled down to a distance of 0.35 m below the unstretched position and released from rest at time t= 0. A graph of the subsequent vertical position y of the lower end of the spring as a function of t is given above, where y= 0 when the spring was initially unstretched. At which time is the upward velocity of the object the greatest?
Answer:
The correct answer will be "0.25 sec".
Explanation:
The graph of the given question is attached below.
According to the graph of the question,
Time,
T = 1 sec
For the upward velocity,
⇒ [tex]t = \frac{T}{4}[/tex]
By putting the value, we get
⇒ [tex]=\frac{1}{4}[/tex]
⇒ [tex]=0.25 \ sec[/tex]
What is the source of almost all energy on Earth?
Earth’s hot core
the Sun
stored carbon
moving water
Answer:
the sun
Explanation:
The sun is the source of almost all energy on Earth beacuse both plants and animal on Earth derive their energy from the sun.
Source of energy on EarthThe Earth is one of the planets that make up the solar system. The Sun is the center of the universe and the Earth revolves round the sun.
The source of almost all energy on Earth is from the sun. The energy from the sun is callled solar energy.
This energy from the sun can be used by the planet to manufatcure its own food. The plants are consumed by animals to provide energy their metabolic activities.
Thus, we can conclude that the sun is the source of almost all energy on Earth beacuse both plants and animal on Earth derive their energy from the sun.
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Two horizontal forces are acting on a box. The box moves only along the x axis. There is no friction between the box and the surface. Suppose that = +5.9 N and the mass of the box is 3.6 kg. Find the magnitude and direction of when the acceleration of the box is +7.1 m/s^2.
Answer:
sorry I don't know I am only in 7th grade
