Answer: [tex]13.4\ m/s[/tex]
Explanation:
Given
The frequency of the source is [tex]f_o=960\ Hz[/tex]
Change in frequency is [tex]75\ Hz[/tex]
Speed of sound [tex]c=343\ m/s[/tex]
Suppose [tex]v[/tex] is the velocity of the observer
Doppler frequency is given by
[tex]f'=f_o\left(\dfrac{c\pm v_o}{c\pm v_s}\right)[/tex]
Here, the source is at rest
While approaching source, frequency is
[tex]f_1=f_o\left(\dfrac{c+v}{c}\right)\quad \ldots(i)[/tex]
While leaving, frequency is
[tex]f_2=f_o\left(\dfrac{c-v}{c}\right)\quad \ldots(ii)[/tex]
The difference in the frequency is
[tex]\Rightarrow f_1-f_2=75\\\\\Rightarrow f_o\left(\dfrac{c+v}{c}\right)-f_o\left(\dfrac{c-v}{c}\right)=75\\\\\Rightarrow f_o\left(\dfrac{2v}{c}\right)=75\\\\\Rightarrow v=\dfrac{75\times 343}{2\times 960}\\\\\Rightarrow v=13.39\approx 13.4\ m/s[/tex]
Suppose that the Department of Energy develops a new reversible engine that has a coefficient of performance (COP) of 4.0 when operated as a refrigerator and a COP of 5.0 when operated as a heat pump. What is its thermal efficiency when operated as a heat engine doing work
Answer:
η = 0.2 = 20%
Explanation:
The relationship between the thermal efficiency of a heat engine and the Coefficient of Performance (COP) of the corresponding Heat Pump is given as follows:
[tex]\eta = \frac{1}{COP_{HP}}[/tex]
where,
η = thermal efficiency = ?
[tex]COP_{HP}[/tex] = Coefficient of Performance of Heat Pump = 5
Therefore,
[tex]\eta = \frac{1}{5} \\\\[/tex]
η = 0.2 = 20%
An observer views four identical objects that are traveling at speeds close to
the speed of light. Can their lengths be used to rank the objects according to
their speeds?
Answer:
D
Explanation:
yes. The shortest object is traveling the fastest.
No,their lengths be used to rank the objects according to their speeds. Because the length of the object is depended on the frame of reference of the observer. Option A is correct.
What is frame of reference?A frame of reference is a mathematical and physical coordinate system whose origin, direction, and scale are given by a collection of reference points.
Because the length of each item is determined by the observer's frame of reference, If an observer is stationary yet traveling at near light speed, he will feel length contraction.
Otherwise, the length of the items should not alter for everyday pace.A spectator sees four identical objects flying at almost the speed of light.
No,their lengths be used to rank the objects according to their speeds. Because the length of the object is depended on the frame of reference of the observer.
Hence,option A is correct.
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The lens labelled (B) has radius 16.5cm on the curved side. Using the shape of the lens to assign the sign of the radius, calculate the focal length of the lens. Give your answer with the correct positive or negative sign using the usual convention for lenses.
Answer:
convex f = 33 cm
concave f = -33 cm
Explanation:
In geometric optics the focal length of a lens is given by
[tex]\frac{1}{f} = ( n-1) \ (\frac{1}{R_2} - \frac{1}{R_1} )[/tex]
where n is the refractive index of the medium, R₁ and R₂ are the focal lengths on each side of the lens.
In this case one of the sides is flat so its focal length is infinite, if the lens is convex the focal length is positive, convergent lens and if it is concave the focal length is negative, divergent lens.
[tex]\frac{1}{f} = (n-1) \ \frac{1}{R}[/tex]
the refractive index of the glass is n = 1.5
let's calculate
1 / f = (1.5 -1) 1 / 16.5
1 / f = 0.03030
f = 33 cm
convex f = 33 cm
concave f = -33 cm
How can a tennis ball and a bowling ball have the same momentum ?
A tennis ball and a bowling ball can have the same momentum. This is because, it depends upon both the mass of object and velocity of object.
What is Momentum?Momentum can be defined as the mass in motion. All objects which have mass so, if an object is moving in space, then it has some amount of momentum which has its mass in motion. The amount of momentum which an object has depend upon two variables which include how much stuff is moving that is the mass of object and how fast the stuff is moving that is the speed.
A fast-moving tennis ball may have the same momentum as a slow-bowling ball. It is important to understand here that the momentum of an object which depends on the product of the mass and velocity of an object, but not the mass or the velocity alone.
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A heater has resistance of 10 ohms. It operates at 120 volts. a. What is the current through the heater?
Answer:
I = 12 A
Explanation:
For this exercise we use the relationship that voltage is proportional to the product of current and resistance
V = I R
I = V / R
let's calculate
I = 120/10
I = 12 A
What is the acceleration of a race car if it has a mass of 1200kg and is moving with an engine force of 400N
Answer:
0.34 m/s^2
Explanation:
force=mass × acceleration
400 =1200 × acceleration
acceleration=400/1200
=0.34 m/s^2
How strong is the repulsive force exerted on two point charges that each carry 1.0 E-6 C of negative charge and are 0.30 meters apart?
Coulomb's Constant is 9.0 E9 N*m2/C2
Remember to identity all of your data, write the equation, and show your work.
F = Kq₁q₂/(r)²
K is a constant
R is the distance between them
F = 9.0 E9 × 1.0 E-6 × 1.0 E-6/(0.30)²
= 9.0E-3/0.30² = 9.0E-3/0.09 = 0.1 N
The electrostatic force of repulsion between two charges can be determined using Coulomb's law of electrostatic force. The force of repulsion between the point charges of magnitude 1 ×10 ⁻⁶ C separated by 0.30 m is 0.1 N.
What is Coulomb's law of electrostatic forces?According Coulomb's law of electrostatic forces, the force between two charges q1 and q2 separated by a distance of r meters is given by the expression:
F = K q1 q2/r²
Where, K is Coulomb's Constant equal to 9.0 ×10⁹ Nm²/C²
Given q1 = q2 = 1 ×10 ⁻⁶ C
r = 0.30 m
k = 9.0 ×10⁹ Nm²/C².
Then the electrostatic force of repulsion between the two point charges is calculated as follows:
F = 9.0 ×10⁹ Nm²/C² × 1 ×10 ⁻⁶ C × 1 ×10 ⁻⁶ C/ (0.30 m )²
= 0.1 N.
Therefore, the repulsive force exerted on two point charges that each carry 1.0 E-6 C of negative charge and are 0.30 meters apart is 0.1 N.
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A cell has an emf of 4,5 V.
8.1 What does this statement mean?
Answer:
it means a cell has 4.5Volt of electromtive force.
A gerbil wheel has a radius of 3.2 inches. The gerbil can spin the wheel at a rate of 35 rotations per minute. Find the angular speed of the wheel in degrees per minute and the linear speed of wheel in inches per minute
Given :
A gerbil wheel has a radius of 3.2 inches. The gerbil can spin the wheel at a rate of 35 rotations per minute.
To Find :
The angular speed of the wheel in degrees per minute and the linear speed of wheel in inches per minute.
Solution :
Angular speed is given by :
[tex]\omega = 25\ rpm \\\\\omega = 25\times 360^o \ per \ minute\\\\\omega = 9000^o \ per \ minute[/tex]
Now, velocity is given by :
[tex]v = Radius\times \dfrac{RPM}{60\ sec/min}\times 2\pi\ rad/rev\\\\v = 3.2 \times \dfrac{35}{60}\times 2\pi\\\\v = 11.73\ m/s[/tex]
Hence, this is the required solution.
A metal with work function 1.17 eV is illuminated with light of wavelength 437 nm. What stopping potential is required for the photoelectrons
Answer: [tex]1.67\ V[/tex]
Explanation:
Given
Work function [tex]\phi =1.17\ eV[/tex]
The wavelength of the light is [tex]\lambda =437\ nm[/tex]
Energy associated with this wavelength is
[tex]E=\dfrac{hc}{\lambda}\\\\\Rightarrow E=\dfrac{1.99\times 10^{-25}}{437\times 10^{-9}}\\\\\Rightarrow E=4.553\times 10^{-19}\ J\\\\\Rightarrow E=2.841\ eV[/tex]
Stopping potential is
[tex]V=\dfrac{E-\phi }{e}\\\\\Rightarrow V=\dfrac{\left(2.841-1.17\right)e}{e}\\\\\Rightarrow V=1.67\ V[/tex]
The diagram shows a toy car on a number line.
A line with arrowheads at both ends has ticks marks every 2 units. The tick marks for 0, 6, and 10 are labeled. A car sits above the tick mark for 2 with a dashed red line leading to the tick mark.
What is the position of the car?
–4
1
2
4
Answer: c.2
Explanation:
Answer:
The Answer is c. 2
Explanation:
I literally just got done with the quiz
Light from a He-Ne laser of wavelength 633 nm passes through a circular aperture. It is observed on a screen 4.0 m behind the aperture. The width of the central maximum is 1.1 cm. What is the diameter of the hole
Answer:
The diameter of the hole is 5.6164 μm
Explanation:
Given the data in the question;
wavelength λ = 633 nm = 633 × 10⁻⁹ m
L = 4.0 M
width of the central maximum D = 1.1 cm.
Now,
Y = D / 2
Y = 1.1 / 2 = 0.55 cm
So diameter of the aperture will be;
α = 1.22λ / ( Y / L )
we substitute in our values;
α = ( 1.22 × (633 × 10⁻⁹ m)) / ( 0.55 / 4.0 )
α = 0.00000077226 / 0.1375
α = 5.6164 × 10⁻⁶ m
α = ( 5.6164 × 10⁻⁶ × 10⁶ ) μm
α = 5.6164 μm
Therefore, the diameter of the hole is 5.6164 μm
Which element would have properties most like helium (He)?
A. Ar
B. Hg
C. H
D. O
Answer: A. Ar
Explanation: not anything else besides Ar
The first law of thermodynamics (which states that energy is conserved) does not specify the direction in which thermodynamic processes in nature can spontaneously occur.
a. True
b. False
Answer:
a. True
Explanation:
The law of conservation of Energy states that energy cannot be destroyed but can only be converted or transformed from one form to another. Therefore, the sum of the initial kinetic energy and potential energy is equal to the sum of the final kinetic energy and potential energy.
Mathematically, it is given by the formula;
Ki + Ui = Kf + Uf .......equation 1
Where;
Ki and Kf are the initial and final kinetic energy respectively.
Ui and Uf are the initial and final potential energy respectively.
The First Law of Thermodynamics is another way to describe the Law of Conservation of Energy. Typically, the First Law of Thermodynamics states that the change of internal energy of a system is equal to the sum of external work and heat spent on the system.
Mathematically, the First Law of Thermodynamics is given by the formula;
ΔU = Q − W
Where;
ΔU represents the change in internal energy of a system.
Q represents the net heat transfer in and out of the system.
W represents the sum of work (net work) done on or by the system.
Hence, the direction in which any thermodynamic process in nature can spontaneously occur isn't stated by the First Law of Thermodynamics.
In an immersion measurement of an odd-shaped metal object, the weight of the object is found to be 980 N when submerged in water. When it is submerged in a heavier Bromine liquid (density 3100 kg/m3), the object weighs 840 N. What is the volume of this object
Answer: [tex]0.00680\ m^3[/tex]
Explanation:
Given
The weight of the object, when submerged in the water is [tex]980\ N[/tex]
When it is submerged in the bromine liquid, it weighs [tex]840\ N[/tex]
Suppose,
[tex]\rho=\text{Density of object}\\\rho_w=\text{Density of water}\\\rho_b=\text{Density of bromine}\\V=\text{Volume of the object}[/tex]
for water,
[tex]\Rightarrow V(\rho -\rho_w)g=980\quad \ldots(i)[/tex]
For bromine
[tex]\Rightarrow V(\rho-\rho_b)g=840\quad \ldots(ii)[/tex]
Divide (i) and (ii)
[tex]\Rightarrow \dfrac{\rho-1000}{\rho-3100}=\dfrac{980}{840}\\\\\Rightarrow 840\rho -840\times 1000=980\rho-980\times 3100\\\\\Rightarrow 140\rho=(3038-840)\cdot 1000\\\\\Rightarrow \rho=15,700\ kg/m^3[/tex]
Put the density value in equation (i)
[tex]\Rightarrow V(15,700-1000)\cdot 9.8=980\\\\\Rightarrow V=\dfrac{100}{14,700}\\\\\Rightarrow V=0.00680\ m^3[/tex]
A child is holding a wagon from rolling straight back down in a driveway that inclined at 20 degree horizontal. if the wagon weigh 150n with what force must the child pull on the handle if the handle is parallel to the incline?
Answer:
F = 51.3°
Explanation:
The component of weight parallel to the inclined plane must be responsible for the rolling back motion of the car. Hence, the force required to be applied by the child must also be equal to that component of weight:
[tex]F = Parallel\ Component\ of\ Weight\ of\ Wagon= WSin\theta\\[/tex]
where,
W = Weight of Wagon = 150 N
θ = Angle of Inclinition = 20°
Therefore,
[tex]F = (150\ N)Sin\ 20^o[/tex]
F = 51.3°
What is the function of an energy source?
1. Stop the flow of electricity
2.Open and close the circuit
3.Begin the flow of electricity
4.Slow down the electrons
13. A tow-truck applies a force of 2,000 N on a 2,000 kg car for a period of 3 seconds. What is the magnitude of
the change in the car's momentum?
Answer:
The Formula is
Change in Momentum = Force * Time
or /\P= F/\t
Plug the numbers into that formula,
P=(2,000N)(3S)
Now Multiply
Your Change in Momentum (Or P) would be 6,000N*s
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The magnitude of the change in the car's momentum = 6000 N.s
What is change in momentum ?The rate of change of momentum is equal to impulse . It is the change in the product of mass and velocity of the body or it can be calculated as force times time period for which force is been applied
Change in momentum = impulse(if change occur for few seconds ) = Force * time period
given
Force = 2000 N
mass = 2000 kg
time = 3 seconds
Change in momentum = 2000 * 3 = 6000 N.s
The magnitude of the change in the car's momentum = 6000 N.s
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As part of a physics experiment, you carry a bathroom scale calibrated in newtons onto an elevator and stand on it. At rest, you check the scale and it reads 588 N. Then the elevator starts accelerating upward at 2.0 m/s2 and you check the reading again. Now what does the scale show
Answer: 708 N
Explanation:
Given
At rest, Elevator reads 588 N
When it starts moving upward at [tex]2\ m/s^2[/tex], apparent weight changes
i.e. weight can be given by
[tex]\Rightarrow W'=m(g+a)\\\Rightarrow W'=mg+mg\cdot \dfrac{a}{g}\\\\\Rightarrow W'=W\left(1+\dfrac{a}{g}\right)\\\\\Rightarrow W'=588\left(1+\dfrac{2}{9.8}\right)\\\\\Rightarrow W'=707.99\approx 708\ N[/tex]
The apparent weight is 708 N
Gold-198 is a radioactive isotope, and it has a half-life of about 2.5 days.
You have 100 grams of Gold-198. How many grams remain after 20 days?
3.125 grams
1.5625 grams
0.78125 grams
0.390625 grams
Answer: 0.390625 grams
Explanation:
A half-life of an element is the amount of time that it takes for half the mass of the element to decay.
Gold-198 having a half-life of 2.5 days therefore means that every 2.5 days, the mass is cut in half.
If there are 20 days, find out how many half-life periods there are:
= 20 / 2.5
= 8 periods
The half life is:
= Original mass * 0.5^number of half-life periods
= 100 * 0.5⁸
= 0.390625 grams
Perhaps the greatest of the Greek astronomers, Hipparchus compiled the first catalog of stars, 49) accurately measured their positions, and defined the basic system of stellar brightnesses which we now call the magnitude system. A particular star in his catalogue has an apparent magnitude of 4 and an absolute -12. Determine the distance to the star.
Answer:
Explanation:
it would be 3 because ju divide 12 by 4
A 400 kg satellite is in a circular orbit at an altitude of 500 km above the Earth's surface. Because of air friction, the satellite eventually falls to the Earth's surface, where it hits the ground with a speed of 1.60 km/s. How much energy was transformed into internal energy by means of air friction
Answer:
E = 1.45 x 10⁹ J = 1.45 GJ
Explanation:
According to the law of conservation of energy:
Potential Energy Lost by Satellite = Kinetic Energy + Internal Energy
[tex]mgh = \frac{1}{2} mv^2 + E\\\\E = mgh - \frac{1}{2} mv^2[/tex]
where,
E = Internal Energy = ?
m = mass = 400 kg
g = acceleration due to gravity = 9.81 m/s²
h = height = 500 km = 500000 m
v = speed on ground = 1.6 km/s = 1600 m/s
Therefore,
[tex]E = (400\ kg)(9.81\ m/s^2)(500000\ m)-\frac{1}{2} (400\ kg)(1600\ m/s)^2\\E = 1.962\ x\ 10^9\ J - 0.512\ x\ 10^9\ J[/tex]
E = 1.45 x 10⁹ J = 1.45 GJ
A train sounds its whistle at a constant frequency as it passes by the platform. Compared to the sound emitted by the whistle, the sound that people on the platform hear as the train moves away has a frequency that is ...
-higher
-the same
-lower
-exactly half
Answer: Higher.
Explanation: The doppler effect essentially. "The Doppler effect can be described as the effect produced by a moving source of waves in which there is an apparent upward shift in frequency for observers towards whom the source is approaching and an apparent downward shift in frequency for observers from whom the source is receding."
What are three ways a driver can cause a car to accelerate?
A. Turn the key in the ignition while the car is stopped.
B. Turn the steering wheel while the car is moving.
C. Press the gas pedal while the car is stopped.
D. Press the brake pedal while the car is moving.
Answer:
B,C,D
Explanation:
Ap3X
a person is sitting on the last bench can see clearly see things written on book but cannot see them distinctly on board. what types of lens is this concave or convex
Answer:
I think concave
Explanation:
A 620 nm light falls on a photoelectric surface and electrons with the maximum kinetic energy of 0.14 eV are emitted. (a) Determine the work function (in eV). eV (b) Determine the cutoff frequency of the surface (in THz). THz (c) What is the stopping potential (in V) when the surface is illuminated with light of wavelength 420 nm
Answer:
(a) The work function is 1.86 eV.
(b) The cut off frequency is 450 THz.
(c) The stopping potential is 1.16 V.
Explanation:
incident wavelength = 620 nm
Kinetic energy, K = 0.14 eV
According to the photoelectric equation
E = W + KE
where, W is the work function, KE is the kinetic energy.
(a) Let the work function is W.
[tex]W = E - KE\\W = \frac{h c}{\lambda }- KE\\W =\frac{6.63\times 10^{-34}\times3\times 10^{8}}{620\times 10^{-9}\times 1.6\times 10^{-19}}-0.14\\\\W =1.86 eV[/tex]
(b) Let the cut off frequency is f.
W = h f
[tex]1.86\times 1.6\times 10^{-19} = 6.63\times 10^{-34}\times f\\f = 4.5\times 10^{14} Hz =450 THz[/tex]
(c) Let the stopping potential is V.
[tex]E = W + eV\\\frac{6.63\times 10^{-34}\times 3\times 10^{8}}{420\times 10^{-9}\times 1.6\times 10^{-19}}=1.8 + eV\\\\V = 1.16 V[/tex]
A 7.5 cm tall Aragorn action figure is placed 12.4 cm in front of a double convex lens. If the image of Aragorn is located 7.5 from the lens, what is the focal length of the lens?
Answer:
f = 4.67 cm
Explanation:
Here, we can use the thin lens formula, as follows:
[tex]\frac{1}{f}= \frac{1}{p}+ \frac{1}{q}\\\\[/tex]
where,
f = focal length of lens = ?
p = distance of object from lens = 12.4 cm
q = distance of image from lens = 7.5 cm
Therefore,
[tex]\frac{1}{f} =\frac{1}{12.4\ cm} +\frac{1}{7.5\ cm}\\\\\frac{1}{f} = \frac{1}{4.67\ cm}[/tex]
f = 4.67 cm
Which of the following is NOT a reason why humans sleep?
Sleep helps to restore and repair brain tissue.
Sleep restores and rebuilds memories.
Sleep provides a psychic safety valve to discharge unacceptable feelings.
During sleep, growth hormone is released, especially in children.
Answer and Explanation:
The answer is the second answer choice. This is because we humans can rebuild or build memories during the day, it doesn't have to happen via sleep.
The first answer choice IS a reason because you aren't working your brain as hard, so your brain has time to heal. A mouse study suggests that sleep helps restore the brain by flushing out toxins that build up during waking hours.
The third answer choice IS a reason because of the idea of Wish Fulfillment: Sigmund Freud suggested that dreams provide a psychic safety valve to discharge unacceptable feelings. The dream's manifest (apparent) content may also have symbolic meanings (latent content) that signify our unacceptable feelings.
The forth answer choice IS a reason because of the idea of Cognitive Development: Some researchers argue that we dream as a part of brain maturation and cognitive development.
#teamtrees #PAW (Plant And Water)
3) A 30 kg child slides freely across a "Slip and Slide" on LEVEL GROUND. While the child slides, the force applied to keep them sliding is 0 N. The coefficient of kinetic friction is 0.02. What is the acceleration experienced by the child?
Answer:
a = 0.1962 m/s^2
Explanation:
The magnitude of kinetic friction exerted is given by
[tex]F_k=\mu_kN[/tex]
Where, μ_k= coefficient of kinetic friction= 0.02 and N = reaction force = mg
Where m= mass = 30 Kg and, g is acceleration due to gravity =9.81 m/s^2
F_k=0.02×30×9.81 =5.886 N
Now, since, there is no applied force this kinetic friction force will cause acceleration of the child
⇒ ma = F_k
here, a is the acceleration
⇒30a = 5.886
⇒ a = 0.1962 m/s^2
A current 2a flows in a circuit fir 2 minutes. Calculate the charge generated in a circuit
Answer:
the charge generated in the circuit is 240 C.
Explanation:
Given;
current flowing in the circuit, I = 2A
time of current flow, t = 2 minutes = 2 x 60s = 120 s
The current flowing through a given circuit is defined as the quantity of charge flowing through the circuit in a given time.
[tex]I = \frac{Q}{t} \\\\Q = I t[/tex]
where;
Q is the charge flowing in the circuit
Q = 2 x 120
Q = 240 C
Therefore, the charge generated in the circuit is 240 C.