Answer:
When friction acts between two surfaces that are moving over each other, some kinetic energy is transformed into heat energy.
A car of mass 2 320 kg is descending a sloping road, inclined at 10.0° to the horizontal. The driver sees a hazard and brakes to make an emergency stop. The distance travelled while braking is 22.5 m.
The initial speed of the car was 13.4 m s−1. Calculate the average braking force. Assume air resistance is negligible.
f = 1.32×10^4 N
Explanation:
We can use the work-energy theorem to find the work done by the braking force f:
W = ∆KE + ∆PE
= (KEf - KEi) + (PEf - PEi)
= [(1/2)mvf^2 - (1/2)mvi^2] + (mhf - mghi)
At the bottom of the slope, vf = 0 and hf = 0 and hi = dsin10° (d = braking distance) so work W becomes
W = -[(1/2)mvi^2 + mgdsin10°]
= -m[(1/2)vi^2 + gdsin10°]
= -(2320kg)[(1/2)(13.4m/s)^2 + (9.8 m/s^2)(22.5m)sin10]
= -2.97×10^5 J
Since W = fd, where f is the braking force, we can now solve for f:
f = W/d = (-2.97×10^5 J)/(22.5 m)
= -1.32×10^4 N
Note: the negative sign means that it is a dissipative force.
Average braking force is 1.32×10^4 N.
What is force?A force in physics is an effect that has the power to alter an object's motion. An object with mass can change its velocity, or accelerate, as a result of a force. An obvious way to describe force is as a push or a pull. A force is a vector quantity since it has both magnitude and direction.
We can use the work-energy theorem to find the work done by the braking force f:
W = ∆KE + ∆PE
= (KEf - KEi) + (PEf - PEi)
= [(1/2)mvf^2 - (1/2)mvi^2] + (mhf - mghi)
At the bottom of the slope, vf = 0 and hf = 0 and hi = dsin10° (d = braking distance) so work W becomes
W = -[(1/2)mvi^2 + mgdsin10°]
= -m[(1/2)vi^2 + gdsin10°]
= -(2320kg)[(1/2)(13.4m/s)^2 + (9.8 m/s^2)(22.5m)sin10]
= -2.97×10^5 J
Since W = fd, where f is the braking force, we can now solve for f:
f = W/d = (-2.97×10^5 J)/(22.5 m)
= -1.32×10^4 N, the negative sign means that it is a dissipative force.
Average braking force is 1.32×10^4 N.
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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
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.
find the cost of running a 60watt for 24hrs. if the electrical energy cost 5 kobo per unit
Answer:
60xtime x cost per unit
Explanation:
...
The Lemon Experiment is a breathing technique.
A) True
B) False
Answer:
b ❤❤❤❤❤❤❤❤❤ yes
Explanation:
yes b❤❤❤❤❤❤❤❤❤❤❤
Answer:
False
Explanation:
Write the term related to reflection of light
(a) The light ray which is incidence (falls) on to a surface is called the Incident ray. (b) The light ray which is reflected (reflects) from a surface is called the Reflected ray. ... (d) The angle made by the Reflected ray with the normal at the point of Reflection is called a Angle of reflection.
The security alarm on a parked car goes off and produces a frequency of 960 Hz. The speed of sound is 343 m/s. As you drive toward this parked car, pass it, and drive away, you observe the frequency to change by 75 Hz. At what speed are you driving
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]
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
he electric field is dependent on the distance between the plates. false: The voltage of a connected charged capacitor decreases when the plate area is increased. false: The voltage of a disconnected charged capacitor increases when the plates are brought closer together.
Answer:
False.
Explanation:
The voltage of a disconnected charged capacitor decreases when the plates are brought closer together because the capacitance is inversely proportional to the area. If the area between plates decreases, its capacitance increases and vice versa. There is direct relationship between voltage of a disconnected charged capacitor and plates. If the distance between plates decreases, the voltage of a disconnected charged capacitor is also decreases while on the other hand, if the distance between plates increases, the voltage of a disconnected charged capacitor is also increases.
A 1.2-kg object moving with a speed of 8.0 m/s collides perpendicularly with a wall and emerges with a speed of 7.2 m/s in the opposite direction. If the object is in contact with the wall for 2.0 ms, what is the magnitude of the average force on the object by the wall
Answer:
480N
Explanation:
Given data
M1= 1.2kg
U1= 8m/s
V1=7.2 m/s
T= 2ms= 0.002
We know that the impulse expression is
P=FT
M(U1-V1)= FT
substitute
1.2(8-7.2)= F*0.002
1.2*0.8= F*0.002
0.96= F*0.002
F= 0.96/0.002
F=480N
Hence the force is 480N
el sistema energético que importancia tiene en el cuerpo
Answer:
De un modo más claro, los sistemas energéticos son los modos que tiene el organismo para suministrar ATP a los músculos. Como decimos, en todos los esfuerzos físicos es necesario contar con la cantidad suficiente de energía y esto viene determinado por la producción de ATP, el adenosin trifosfato.
In an electromagnet, why must the wire be connected to the battery for the magnet to work?
Answer:
Some of the copper wire needs to be exposed so that the battery can make a good electrical connection. ... You need to do this because the direction of a magnet field depends on the direction of the electric current creating it. The movement of electric charges creates a magnetic field.
Explanation:
In an electromagnet, it must the wire be connected to the battery for the magnet to work the current is flowing through into the wire once it is introduced.
What is a magnetic field?The magnetic field is defined as the field the magnetic materials generate or when an electric charge moves in a field region that generates the magnetic field.
As we know, the electricity is often used to generate a magnetic field in electromagnets.
The current is flowing through into the wire once it is introduced, from either a battery or maybe another source of electricity. The looped wire is magnetized as if it were a magnetic material as a function of the magnetic field created around it.
Thus, in an electromagnet, it must the wire be connected to the battery for the magnet to work the current is flowing through into the wire once it is introduced.
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A teacher sets up the following demonstration in which he places a clear glass rod with an index of refraction of 1.47 into a beaker containing an unknown liquid. When he does this, the submerged portion of the glass rod seems to disappear. The teacher gives the students the following list of possible liquids in which this glass rod has been submerged.
Material Index of Refraction
Salt Water 1.37
Glycerin 1.47
Silicon Oil 1.52
Required:
Which material is most likely to represent the liquid in the beaker and why?
Answer:
salt water
total internal reflection
Explanation:
Let's analyze this experiment, for the rod to disappear it must have happened that the light coming from it does not reach us that we are seeing from the air n = 1, therefore the light from the rod must be reflected, for this to happen we use the refractive ratio
n₁ sin θ₁ = n₂ sin θ₂
where n₁ is the refractive index of the rod, the greatest angle that could exist in the liquid is 90º, therefore sin 90 = 1
n₁ sin θ₁ = n₂
sin θ₁ = n₂ /n₁
the only way this expression is correct is that
n₂ <n₁
that is
n₂ < 1.47
When reviewing the given materials, the only one that meets this condition is salt water by the total internal reflection
The speed of any wave depends on ...
-its angle of reflection
-its amplitude
-its energy
-the medium through which it travels
Answer:
the medium through which it travels
Explanation:
A golf club hits a 0.0459 kg golf ball at rest; the club is in contact with the ball for 0.00138 s. Afterwards the ball leaves at 63.9 m/s. How much force acted on the ball? (Unit = N)
Answer: 2120 N is correct
Explanation: correct answer for acellus
You are reading a book and decide to estimate the magnitude of the electric and magnetic fields of the light that is incident on the book from your desk lamp. You can treat the lamp as a point source that emits sinusoidal EM waves uniformly in all directions. The book is at 1 m from the 100 Watt light bulb. Assume that all the electric energy is transformed into visible light.
(Part a) Calculate I, the intensity of the light incident on your book?
(Part b) Find Eo and Bo, the amplitude of the electric and the magnetic fields of the EM waves emitted by the lamp.
Answer:
a. 7.96 W/m² b. i. 0.205 V/m ii. 0.68 nT
Explanation:
(Part a) Calculate I, the intensity of the light incident on your book?
Intensity, I = Power, P/Area,A
I = P/A where P = 100 W and A = 4πr² where r = distance of source from book = 1 m.
So, I = P/A
= 100 W/4π(1 m)²
= 25/π W/m²
= 7.96 W/m²
(Part b) Find Eo and Bo, the amplitude of the electric and the magnetic fields of the EM waves emitted by the lamp.
i. Eo the amplitude of the electric field
Intensity, I = E²/cμ₀ where E = r.m.s value of electric field, c = speed of light = 3 × 10⁸ m/s and μ₀ = permeability of free space = 4π × 10⁻⁷ H/m
Thus, E = √(I/cμ₀)
substituting the values of the variables into the equation, we have
E = √(I/cμ₀)
E = √(7.96 W/m²/[3 × 10⁸ m/s × 4π × 10⁻⁷ H/m])
E = √(7.96 W/m²/120π H/s)
E = √(0.0211 Ws/Hm²)
E = 0.145 V/m
Now E = E₀/√2 where E₀ = maximum value of electric field
So, E₀ = √2E
= √2 × 0.145 V/m
= 0.205 V/m
ii. Bo the amplitude of the magnetic field
Since c = E₀/B₀ where c = speed of light = 3 × 10⁸ m/s
B₀ = E₀/c
= 0.205 V/m ÷ 3 × 10⁸ m/s
= 0.068 × 10⁻⁸ T
= 0.68 × 10⁻⁹ T
= 0.68 nT
What is the momentum of a 12 kg ball
travelling at 35 m/s?
Answer:
The answer is 420kgm/s
Explanation:
momentum = mass×velocity
= 12kg×35m/s
=420kgm/s
Answer:
ligma
Explanation:
b) What are the only two sources of energy that produce all the energy we use on Earth? What form
of energy does each of these sources use?
Answer:
Solar and nuclear power generate more than 99 percent of our civilization's energy. Every other important source of energy is a combination of these two. The majority of them are solar in nature. We discharge previously collected solar energy when we burn wood.
and
Nuclear energy, fossil energy (oil, coal, and natural gas), and renewable energy (wind, solar, geothermal, and hydropower) are all examples of primary energy sources.
Explanation:
A 10- kg ball starting from rest rolls down a 5 m tall smooth hill from one person to another person who is standing at the bottom of the hill with a big spring whose constant is 100 N/m. How far does the spring compress in order to stop the ball
Answer: 3.13 m
Explanation:
Given
mas of the ball is m=10 kg
The ball rolls down a vertical distance of 5 m
Spring constant of spring is [tex]k=100\ N/m[/tex]
Here, the potential energy of the ball converted into kinetic energy which in turn converts into elastic potential energy
[tex]\Rightarrow mgh=\frac{1}{2}kx^2\quad [\text{x=compression in the spring}]\\\\\Rightarrow 10\times 9.8\times 5=\frac{1}{2}\cdot 100\cdot x^2\\\Rightarrow x=\sqrt{9.8}\\\Rightarrow x=3.13\ m[/tex]
Thus, the spring compresses by 3.13 m.
True or False: Buoyancy is an upwards force measured in Newtons.
Answer:
true
Explanation:
Buoyancy is an upwards force measured in Newtons is true.
What is force?A force is an effect that can alter an object's motion according to physics. An object with mass can change its velocity, or accelerate, as a result of a force. An obvious way to describe force is as a push or a pull. A force is a vector quantity since it has both magnitude and direction.
Upthrust, often known as buoyancy, is an upward force applied by a fluid against the weight of an object that is partially or completely submerged. The weight of the fluid on top causes pressure in a fluid column to rise with depth.
Buoyancy is an upwards force measured in Newtons is true.
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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°
You are studying a population of flowering plants for several years. When you present your research findings you make the statement that, "Increased allocation of resources to reproduction relative to growth diminished future fecundity." Which of the following graph descriptions could accurately present your data?
a) With seeds in the current year on the y-axis and seeds in the previous year on the x-axis, you would see a line that increased from left to right
b) With survivorship on the y-axis and number of seeds produced on the x-axis, you would see a line that decreased left to right.
c) With leaf area on the y-axis and number of seeds produced on the x-axis, you would see a line that increased left to right
d) With survivorship on the y-axis and number of seeds produced on the x-axis, you would see a line that increased left to right.
e) With seeds in the current year on the y-axis and seeds in the previous year on the x-axis, you would see a line that decreased from left to right
Answer:
Option A
Explanation:
The graph for this problem must depict the following ""Increased allocation of resources to reproduction relative to growth diminished future fecundity."
Hence, the survivor ship must be on the Y axis and the resources on the X axis.
Here the resources include the number of seeds produced.
hence, the higher is the number of seeds (resource), the lower is the survivorship (future fecundity)
Hence, option A is correct
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."
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 chocolate brownie has a volume of 360cubic centimeters and a mass of 270grams. Calculate its density.
Write your answer to the hundredths place.
Answer:
Its density is 0.75 grams per cubic centimeters.Explanation:
Given that:
A chocolate brownie has a volume of 360 cubic centimeters and a mass of 270 grams.To Calculate:
Its density.We know that:
Density = Mass/VolumeWe have:
Mass = 270 gVolume = 360 ccFinding its density:
⟶ Density = 270/360
⟶ Density = 0.75
Hence,
Its density is 0.75 g/cc.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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10 A particle in circular motion performs 30 oscillations in 6
seconds. Its angular velocity is?
Explanation:
Let omega = angular velocity (in rad/s). Then
omega = (# of oscillations)/(6 s)
= (30 osc)/(6 s) = 5 osc/s
We need to convert this to rad/s:
omega = (5 osc/s)(2π rad/osc)
= 10π rad/s
= 31.4 rad/s
What are the biotic factors in this image?
Someone help thank you!!
PLEASE HELP!! WILL GIVE POINTS
A machine does 9,800 joules of work to life a couch twenty meters off the ground. What is the is mass of the couch?
Answer:
49 kg is the mass of the couch.
Explanation:
GPE = mgh
9800 = m * 10 * 20
9800 = 200m
m = (9800/20) = 49 m
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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