Answer:
b
Explanation:
A whistle emitting a note of 4 kHz is
whirled in a horizontal circle of radius 1 m at a constant speed. If the highest note heard
by a person a large distance away is 4200 Hz, find:
(i) the speed of the whistle
(ii) the lowest note heard by the person,
(iii) the time taken for the whistle to make on complete revolution,
(iv) the time interval between the person hearing the highest and lowest note.
Answer:
(i) The speed of the whistle is 16.[tex]\overline 3[/tex] m/s
(ii) The lowest note heard by the person is 3,818.[tex]\overline{18}[/tex] Hz
(iii) The time taken for the whistle to make one revolution is approximately 0.38468 seconds
(iv) The time interval between the person hearing the highest and lowest note is approximately 0.19234 seconds
Explanation:
The question relates to the Doppler effect for which the change in frequency is given as follows;
[tex]f_L = \left ( \dfrac{v \pm v_L }{v \pm v_S} \right ) \cdot f_S[/tex]
Where;
[tex]f_L[/tex] = The frequency heard by the listener
v = The speed of sound in air = 343 m/s
[tex]v_L[/tex] = The listener's speed
[tex]v_S[/tex] = The source's (whistle) speed
[tex]f_S[/tex] = The frequency of the source
The given parameters are;
The frequency of the whistle (source), [tex]f_S[/tex] = 4 kHz = 4,000 Hz
The radius of the horizontal circle around which the whistle is whirled = 1 m
The highest note heard by a person a large distance away = 4200 Hz
The distant listener is taken as stationary, [tex]v_L[/tex] = 0 m/s
We therefore have;
[tex]f_L = \left ( \dfrac{v \pm 0 }{v \pm v_S} \right ) \cdot f_S = \left ( \dfrac{v }{v \pm v_S} \right ) \cdot f_S[/tex]
(i) When the whistle's motion while it is being whirled towards the listener, [tex]v_S[/tex] is negative
When the whistle's motion while it is being whirled is away from listener, [tex]v_S[/tex] is positive
The highest note, [tex]f_{LH}[/tex], is obtained with the lowest denominator, that is when the source moves towards the listener and [tex]v_S[/tex] is negative, we get;
[tex]f_{LH} = 4,200 \ Hz = \left ( \dfrac{343 \ m/s }{343 \ m/s - v_S} \right ) \times 4,000 \ Hz[/tex]
[tex]\dfrac{4,200 \ Hz}{4,000 \ Hz} = \dfrac{21}{20} = \dfrac{343 \ m/s}{343 \ m/s - v_S}[/tex]
21·(343 m/s - [tex]v_S[/tex]) = 20×343 m/s
21 × [tex]v_S[/tex] = 21 × 343 m/s - 20 × 343 m/s = 343 m/s
[tex]v_S[/tex] = (343 m/s)/21 = 49/3 m/s = 16.[tex]\overline 3[/tex] m/s
The speed of the source = The speed of the whistle
∴ The speed of the source = [tex]v_S[/tex] = 16.[tex]\overline 3[/tex] m/s = The speed of the whistle
(ii) The lowest note heard by the person occurs when the denominator of the formula for the change in frequency is smallest for which we have the value of [tex]v_S[/tex] as positive and the source moves away from the observer which is presented as follows;
[tex]f_{LH} = \left ( \dfrac{343 \ m/s }{343 \ m/s +16.\overline 3 \ m/s } \right ) \times 4,000 \ Hz = 3,818.\overline {18} \ Hz[/tex]
The lowest note heard by the person = 3,818.[tex]\overline{18}[/tex] Hz
(iii) The angular velocity of the whistle, ω is given as follows;
[tex]\omega = \dfrac{\theta}{t} = \dfrac{v_S}{r} = \dfrac{16. \overline 3 \ m/s}{1 \ m} = 16. \overline 3 \ radians/second[/tex]
The angle rotated in one revolution, is 2·π radians, therefore, when θ = 2·π radians, the time, [tex]t_c[/tex], to complete one revolution is given as follows;
[tex]t_c = \dfrac{\theta}{\omega} = \dfrac{2 \times \pi \ radians}{16. \overline 3 \ radians/second} \approx 0.385 \ seconds[/tex]
Therefore, the time to complete one revolution ≈ 0.38468 seconds
(iv) The time interval between the person hearing the highest and lowest note is the time to complete half a cycle ≈ 0.38468/2 seconds ≈ 0.19234 seconds.
A monkey pushes a rock horizontally on a frictionless table with a net force of 10 N for 2.0 m. How much kinetic energy does the rock gain?
Round the answer to two significant digits
Answer:
The answer is 20J
Explanation:
PSYCHOLOGY
The most widely used psychoactive drug is
ОА.
heroin.
B.
caffeine.
O C.
PCP.
O D.
LSD.
the answer is B.caffeine. Just didn’t see anyone have this question on Brainly yet.
d is the right answer
slader How much energy is required to move a 1040 kg object from the Earth's surface to an altitude four times the Earth's radius
Answer:
ΔU = 5.21 × 10^(10) J
Explanation:
We are given;
Mass of object; m = 1040 kg
To solve this, we will use the formula for potential energy which is;
U = -GMm/r
But we are told we want to move the object from the Earth's surface to an altitude four times the Earth's radius.
Thus;
ΔU = -GMm((1/r_f) - (1/r_i))
Where;
M is mass of earth = 5.98 × 10^(24) kg
r_f is final radius
r_i is initial radius
G is gravitational constant = 6.67 × 10^(-11) N.m²/kg²
Since, it's moving to altitude four times the Earth's radius, it means that;
r_i = R_e
r_f = R_e + 4R_e = 5R_e
Where R_e is radius of earth = 6371 × 10³ m
Thus;
ΔU = -6.67 × 10^(-11) × 5.98 × 10^(24)
× 1040((1/(5 × 6371 × 10³)) - (1/(6371 × 10³))
ΔU = 5.21 × 10^(10) J
Only about 50% of the solar energy directed toward Earth penetrates directly to the surface. Explain what happens to the rest of the radiation.
Answer:
it is absorbed or reflected by the atmosphere
Explanation:
In the case when approx 50% only of the solar energy would be directed towards earth and it would be penetrates directly to the surface so the rest or remaining of the radiation would be either absorbed or refected by the atmosphere
So as per the given situation the above represent the answer
hence, the same is to be considered and relevant
A hollow glass prism doesnot cause the dispersion of light why?
Please HELP! Its urgent..
Answer:
When white light passes through the prism ,different colours suffers deviation through different angles and light appears to be dispersed. But in a hollow prism dispersion does not take place as all the colours travel with same speed in the air inside hollow prism. Thus no angular dispersion is there.
Electric field lines can never cross. What would crossed electric field lines indicate?
a field pointing in two directions
an attractive force on a charge
a nonuniform area of the field
a place where the field strength is zero
Answer:
It indicates that a force has 2 directions at the point at which they cross
Answer:
A. A field pointing in two directions
Select the correct answer.
The goal of the Tariff of Abominations, passed in 1828, was to protect the industries in the
foreign nations. Which statement best shows the effect of this tariff on American history?
ОА.
The Tariff of Abominations widened Income Inequality because it favored the
ОВ.
The Tariff of Abominations upset American Indians because it did nothing pro
OC.
The Tariff of Abominations caused conflicts between the North and the South
OD
The Tariff of Abominations upset common working class Americans because i
Reset
Next
Answer:
OC, The Tariff of Abominations caused conflicts between the North and the South regarding their sectional interests.
Explanation:
The Tariff of Abominations did cause conflicts because it widened income inequality since it favored the rich upper class while burdening the lower class. The South was the lower class, and the North was more of the upper class.
help with this pleaseeee i’ll give brainlist:)
Answer:
C. Test to see if your material is strong and works well.
Pollen grains help scientists
identify plants and make assumptions on past climate conditions.
understand tree growth and make assumptions on past climate conditions.
understand how Earth was shaped and make assumptions on past climate conditions.
identify major ice ages and make assumptions on past climate conditions.
Answer:
A. identify plants and make assumptions on past climate conditions.
Explanation:
Answer was right on my Edge quiz!
Pollen grains help scientists identify plants and make assumptions on past climate conditions.
WHAT IS PROXY CLIMATE?Proxy climate is climate inferred from past records i.e. not current.
Proxy climate makes use of proxy climate data also called proxies. These proxies help in inferring about the past climate.
Examples of proxies are;
pollen grainsCoral reefsIce coresTherefore, pollen grains help scientists identify plants and make assumptions on past climate condition.
Learn more about past climate at: https://brainly.com/question/9328022
Item 1 Circuit A has a resistance of 7.5 ohms, and circuit B has a resistance of 5 ohms. Which statement about the circuits must be correct? (1 point) Item 2 Item 3 If the current in circuit A is less than the current in circuit B, then the voltage in circuit A is less than the voltage in circuit B. Item 4 If the voltage of circuit A is equal to the voltage of circuit B, then the current in circuit A is less than the current in circuit B. If the current in circuit A is equal to the current in circuit B, then the voltage in circuit A is less than the voltage in circuit B. If the voltage of circuit A is equal to the voltage of circuit B, then the current in circuit A is equal to the current in circuit B. 0 Type here to search е c
Answer:
e4atetetsgts4tgesetse
Explanation:
ger54ttagcuit B, then the voltage in circuit A is less than the voltage in circuit B. Item 4 If the voltage of circuit A is equal to the voltage of circuit B, then the current in circuit A is less than the current in circuit B. If the current in circuit A is equal to the current in circuit B, then the voltage in circuit A is less than the voltage in circuit B. If the voltage of circuit A is equal to the voltage of circuit B, then the current in circuit A is equal to the current in circuit B. 0 Type here to search е c
A ______ measurement that both size and direction may be represented by an arrow
Answer:
Vector
Explanat
Vector is the only right answer in the situatuin
Fred spends most Sunday afternoons watching pro football games and consuming large quantities of
food. What effect does this practice have upon his inertia? Explain.
I
Answer:
His inertia increases.
Explanation:
Inertia is defined as the force which keeps stationary objects to stay still (remain at rest) or moving objects in motion at the same speed and in the same direction unless it is stopped by an external force. It can also be defined as the resistance of an object to resist change by remaining in its state of rest or in motion. Therefore, his inertia increases.
A book is resting on the table. Forces are exerted _____.
upward by the table
downward by the book
in equal and opposite directions
all of the above
Answer:
downward by the book
Explanation:
because of gravity
A 55 kg roller skater is at rest on a flat skating rink, a 198 N horizontal force is needed to set the skater in motion.
However, after the skater is in motion a horizontal force of 175 N is necessary to overcome the friction of 52N to keep
the skater moving at a constant velocity. Find the coefficient of kinetic friction.
Answer:
Explanation:
To get the person Moving you have to overcome the static (means not moving) friction coefficient. U(static)
To get the person going at the same speed you have to overcome the kinetic friction coefficient. U(Kinetic)
Force to get him moving is 198 N. Force = ma = U(static)Mg
combining the 2 equations you get 198N = U(static)* 55kg *9.8m/s^2 Solve for U(static)
Same equation to keep him moving except with the dynamic force and the dynamic U
175N= U(kinetic)*55kg*9.8m/s^2 Solve (U dynamic)
Newton's second law and the expression of the friction force allow to find the result for the value of the kinetic friction coefficient is:
μ = 0.325
Newton's second law establishes a relationship between the net force, mass, and acceleration of the body.
Σ F = m a
Where the bold letters indicate vectors, m is the mass and the acceleration.
The friction force is a macroscopic force that represents the interactions between the two surfaces, it can be of two types:
Static. If there is no relative movement between the two surfaces. Kinetics. If there is relative movement between the two surfaces.The expression in both cases is:
fr = μ N
Where N is the normal and μ is the friction coefficient, one value for the static case and another for the kinetic case.
In the attachment we have a free-body diagram for when the skater is moving with constant speed.
y=axis
N - W = 0
N = W
x-axis
F - fr = 0
F = fr
They indicate that the applied force is F = 175N and the mass of the skater is m = 55 kg.
We substitute.
F = μ mg
μ = [tex]\frac{F}{mg}[/tex]
Let's calculate.
μ =[tex]\frac{175}{55 \ 9.8}[/tex] 175/55 9.8
μ = 0.32
In conclusion, using Newton's second law and the expression of the friction force we can find the result for the value of the coefficient of kinetic friction is:
μ = 0.325
Learn more here: brainly.com/question/1714663
Which Newton’s law is shown below?
First
Second
Third
Pls answer
Answer:
This is Newton's first law.
Explanation:
An object in motion will stay in motion and an object at rest wI'll stay at rest unless acted upon by an unbalanced force.
What element does the picture represent? (Use the periodic table if you need to) *
(1 Point)
nitrogen
O chlorine
O oxygen
What units are used to measure mass and weight?
WILL GIVE LOTS OF POINTS!!!!!!
Explain the process of convection in the atmosphere.
Answer : Convection is a major factor in weather. The sun heats the earth's surface, then, when cooler air comes into contact with it, the air warms and rises, creating an upward current in the atmosphere. That current can result in wind, clouds, or other weather.
Explanation:
In the atmosphere convection happens when warm air on the ground rises into the atmosphere(clouds) and at the high altitudes the air becomes cold causing the air to come back down to the surface.
HELP I'M LAZY AND D U M B
(please use information from the small text to answer the questions)
1. What do the curved blue lines wrapping around Earth represent?
2. The geomagnetic poles move over time. What causes this to happen?
3. How do Earth's geomagnetic poles differ from its geomagnetic poles?
4. Mars has a week magnetic field. How do you think the conditions on the surface of Mars compare with those on Earth? What would that mean for astronauts traveling to Mars in the future?
Maps can convey a lot of different types of information. They can tell you where you are or they can tell you something about a location. Earth scientists often use maps that have coordinates so that they can locate themselves or the features they are interested in. Different types of maps show different things well. For example, some types of maps show the tropical areas really well but do a terrible job depicting the polar regions.
Weight is the direct result of :
A. Distance
B. The amount of gravity being pulled
Pangaea was not the first, nor will it be the last, super continent. In the process of continental drift, sometimes chunks of continents disappear. Describe how this can happen.
Answer:
Explanation:
there could be earthquakes or the tectonic plates under can make it fall apart, natural disasters
hope this helps!!
“Energy is never created of destroyed, it only transforms from one form to another” is the definition of…
A. The Law of Diminishing Returns
B. The Law of Conservation of Energy
C. The Law of Universal Gravitation
D. The Law of Entropy
Answer:
it is B. The Law of Conservation of Energy
Explanation:
hope this helps
Mass varies depending on where the object is located.
True or false
when a person holds a ball above earth's surface, where is this potential energy stored?
Answer:
in the ball
Explanation:
potential energy is where an object has energy, always, but it isn't always moving, and when you drop the ball, it has kinetic energy.
The stone, which weighs 400 g, is thrown upwards at a speed of 20 m / s. Climbed to a height of 12 m. Determine: what is equal to the work of the resistance force; equal to the mean resistance force?
Given that,
Mass of the stone, m = 400 g = 0.4 kg
Initial speed, u = 20 m/s
It is climbed to a height of 12 m.
To find,
The work done by the resistance force.
Solution,
Let v is the final speed. It can be calculated by using the conservation of energy.
[tex]v=\sqrt{2gh} \\\\v=\sqrt{2\times 9.8\times 12} \\\\v=15.33\ m/s[/tex]
Work done is equal to the change in kinetic energy. It can be given as follows :
[tex]W=\dfrac{1}{2}m(v^2-u^2)\\\\=\dfrac{1}{2}\times 0.4\times (15.33^2-20^2)\\\\=-32.99\ J[/tex]
So, the required work done is 32.99 J.
a carbon atom with 6 proton and 6 neutron in its nucleus is called carbon-12 the carbon atom with 8 neutrons is called what
Answer:
carbon-14 must be the answer
What is most likely to happen during deposition?
Answer:
a person appears at a specified time and place and gives sworn testimony
Explanation:
Hope this helps
An LDR was placed near a light source. The following results were
recorded: potential difference = 5.50V current = 12.5 mA. Which equation
links current, potential difference and resistance? *
Answer:
V = 440I
Explanation:
According to ohm's law which states that the current passing through a metallic conductor at constant temperature is directly proportional to the potential difference across its ends.
Let V be the potential difference
I is the current
R is the resistance
Mathematically;
V∝I
V = IR
Given
Potential difference V = 5.50Volts
Current = 12.5mA = 12.5*10^-3A
Current I = 0.0125A
Recall that V = IR
R = V/I
Substitute the given parameters into the formula;
R = 5.50/0.0125
R = 440 ohms
Hence the equation that links current, potential difference and resistance is expressed as;
V = I(440)
V = 440I
in an effort to reach the store before it closed the motorist increase the speed of his car from 20 m per second to 60 meters per second over a four second. What was the car's acceleration
Answer:
10
Explanation:
Givens
vi = 20 m/s
vf = 60 m/s
t = 4 second.
Formula
a = (vf - vi) / t
a = (60 - 20)/4
a = 40 / 4
a = 10 m/s^2