Answer:
C. A heat engine must deposit some energy in a cold reservoir.
Explanation:
The second law of thermodynamics says that "It is impossible to extract an amount of heat Q from a hot reservoir and use it all to do work W. Some amount of heat q must be exhausted to a cold reservoir."
This means that if we extract an amount of heat Q from the hot reservoir, the work W can never be exactly equal to Q, then there is a surplus of heat q that must be deposited in a cold reservoir.
Then we have the equation:
Q = W + q
From this we can conclude that the correct option is:
C. A heat engine must deposit some energy in a cold reservoir.
There will be always some energy that is not transformed into work, and is deposited in a cold reservoir.
C. A heat engine must deposit some energy in a cold reservoir.
The second law of thermodynamics says that "It is impossible to extract an amount of heat Q from a hot reservoir and use it all to do work W. Some amount of heat q must be exhausted to a cold reservoir". This means that if we extract an amount of heat Q from the hot reservoir, the work W can never be exactly equal to Q, then there is a surplus of heat q that must be deposited in a cold reservoir. Then we have the equation: Q = W + q There will be always some energy that is not transformed into work, and is deposited in a cold reservoir.Therefore, option C is correct.
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Cecily is inflating her bicycle tyre with the pump below. When she pushes the plunger down, it is doing work against the gas. This means that the plunger is transferring what to the gas particles?
The plunger is transferring energy to the gas particles.
What the plunger is transferring to the gas particles?When Cecily is applying pressure to the plunger, the gas inside is being compressed, and the speed of gas molecules increases.
When these air molecules enter the tire, adiabatically, the temperature of the gas rises.
It happens due to an increase in the average kinetic energy of the gas particles.
Thus, the gas particles receive energy from the plunger.
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On a slope where does a marble have to most kinetic energy?
a) it is always the same
b) at the initial position
c) at the final position
d) somewhere between the initial and the final position
Answer:
C
Explanation:
Kinetic energy is the energy of motion. It has the most potential energy at the top but the most kinetic at the bottom after it's accelerated fully down the slope.
. What is the atomic number for calcium?
A bicycle racer rides from a starting marker to a turnaround marker at 10 m/s. She then rides back along the same route from the turnaround marker to the starting marker at 16 m/s. What is her average speed for the whole race?
Answer:
12.31 m/s
Explanation:
If we recall from the previous knowledge we had about speed,
we will know that:
speed = distance/ time.
As such:
The average speed of the rider bicycle is
average speed = total distance/ total time
Mathematically, it can be computed as:
[tex]v_{avg} = \dfrac{d+d}{\dfrac{d}{v_1}+ \dfrac{d}{v_2}}[/tex]
[tex]v_{avg} = \dfrac{2d}{\dfrac{d}{10 \ m/s}+ \dfrac{d}{16 \ m/s}}[/tex]
[tex]v_{avg} = \dfrac{2}{\dfrac{1}{10 \ m/s}+ \dfrac{1}{16 \ m/s}}[/tex]
[tex]v_{avg} = \dfrac{2}{\dfrac{13}{80 \ m/s}}[/tex]
[tex]\mathbf{v_{avg} =12.31 \ m/s}[/tex]
describe measurement in our daily life
discuss how devastating a 7.7 - magnitude earthquake is.
Answer:
Explanation:
It’s devastating because when a earthquake is 7.7 magnitude the
A basketball is picked up off the ground and carried to the top of a platform that is 160 feet up. It is then dropped to the ground. The ball rebounds one-half the height each time it hits the ground. What is the total vertical distance the ball will travel from the moment it is picked up to the moment it reaches its maximum height after the fourth bounce
Answer:
Explanation:
The total distance travelled by ball before first bounce
= 160 + 160 = 320 ft
Distance travelled between first bounce and second bounce
= 80 + 80 = 160 ft
Distance travelled between second bounce and third bounce
= 40 + 40 = 80 ft
Distance travelled between third bounce and fourth bounce
= 20 + 20 = 40 ft .
Distance travelled in fourth bounce = 10 ft
Total distance travelled = 320 + 160 + 80 + 40 + 10
= 610 ft .
What is one characteristic of an electron?
Answer:
A is the best character that defines an electron.
If an object has applied force of 20 N and a frictional force of 5 N what is the net force?
Answer:
Net force = 15 N
Explanation:
Given that,
Applied force on an object = 20 N
Frictional force = 5 N
We need to find the net force acting on the object.
Friction is an opposing force. It acts in the opposite direction.
Net force = Applied force - Frictional force
= 20 N - 5 N
= 15 N
Hence, the net force acting on the object is 15 N.
what is the pressure on a swimmer 50 m below the surface of a lake
Answer:
P = 490500 [Pa]
Explanation:
The pressure at the bottom of a vessel and even of a lake or sea can be calculated by means of the following hydrostatic equation.
[tex]P=Ro*g*h[/tex]
where:
P = pressure [Pa] (units of pascal)
Ro = water density = 1000 [kg/m³]
g = gravity acceleration = 9.81 [m/s²]
h = elevation = 50 [m]
Now replacing:
[tex]P=1000*9.81*50\\P=490500[Pa][/tex]
3.
What is a star? Why does the sun appear so big whereas the other stars do not?
Ans.
A student places an object with a mass of m on a disk at a position r from the center of the disk. The student starts rotating the disk. When the disk reaches a speed of 0.8 m/s, the object starts to slide off the disk. What is the coefficient of static friction between the object and the disk?
mass=100 g, r= 0.75 m
Answer:
The coefficient of static friction between the object and the disk is 0.087.
Explanation:
According to the statement, the object on the disk experiments a centrifugal force due to static friction. From 2nd Newton's Law, we can represent the object by the following formula:
[tex]\Sigma F_{r} = \mu_{s}\cdot N = m\cdot \frac{v^{2}}{R}[/tex] (1)
[tex]\Sigma F_{y} = N - m\cdot g = 0[/tex] (2)
Where:
[tex]N[/tex] - Normal force from the ground on the object, measured in newtons.
[tex]m[/tex] - Mass of the object, measured in newtons.
[tex]g[/tex] - Gravitational acceleration, measured in meters per square second.
[tex]v[/tex] - Linear speed of rotation of the disk, measured in meters per second.
[tex]R[/tex] - Distance of the object from the center of the disk, measured in meters.
By applying (2) on (1), we obtain the following formula:
[tex]\mu_{s}\cdot m\cdot g = m\cdot \frac{v^{2}}{R}[/tex]
[tex]\mu_{s} = \frac{v^{2}}{g\cdot R}[/tex]
If we know that [tex]v = 0.8\,\frac{m}{s}[/tex], [tex]g = 9.807\,\frac{m}{s^{2}}[/tex] and [tex]R = 0.75\,m[/tex], then the coefficient of static friction between the object and the disk is:
[tex]\mu_{s} = \frac{\left(0.8\,\frac{m}{s} \right)^{2}}{\left(9.807\,\frac{m}{s^{2}} \right)\cdot (0.75\,m)}[/tex]
[tex]\mu_{s} = 0.087[/tex]
The coefficient of static friction between the object and the disk is 0.087.
Sultan travels 40 km north then 60 km west to reach the stadium and watch the football match. What
is Sultan's displacement?
Answer:
sultan's displacement is
[tex]20 \sqrt{13} [/tex] km
If a woman walks at a speed of 5 miles/hour for 3 hours, she will have walked how many miles?
The distance walked by the woman at the given speed an time, is 15 miles.
What is meant by speed?The speed of an object is defined as the rate of change of the distance travelled by the object.
Here,
Speed with which the woman is walking,
v = 5 miles/hour
Time taken by the woman for walking,
t = 3 hours
We know speed is the rate of change of distance,
v = d/t where d is the distance travelled by the woman
So, d = v x t
d = 5 x 3
d = 15 miles
Hence,
The distance walked by the woman at the given speed an time, is 15 miles.
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Q1. A man wants to install a surveillance mirror in his shop, which mirror should he use?(1)
a) Convex mirror
b) Concave mirror
c) Plane mirror
d) Both (a) and (b)
answer is convex mirror
Explanation:
A
Because convex mirror will provide maximum view
Two point charges have a total electric potential energy of -24 J, and are separated by 29 cm.
If the total charge of the two charges is 45 μC, what is the charge, in μC, on the positive one?
What is the charge, in μC, on the negative one?
Answer:
The charge of the negative one is 13.27 microcoulombs and the positive one has a charge of 58.27 microcoulombs.
Explanation:
Electric potential energy between two point charges is derived from concept of Work, Work-Energy Theorem and Coulomb's Law and described by the following formula:
[tex]U_{e} = \frac{k\cdot q_{A}\cdot q_{B}}{r}[/tex] (1)
Where:
[tex]U_{e}[/tex] - Electric potential energy, measured in joules.
[tex]q_{A}[/tex], [tex]q_{B}[/tex] - Electric charges, measured in coulombs.
[tex]r[/tex] - Distance between charges, measured in meters.
[tex]k[/tex] - Coulomb's constant, measured in kilogram-cubic meters per square second-square coulomb.
If we know that [tex]U_{e} = -24\,J[/tex], [tex]q_{A} = 45\times 10^{-6}\,C+ q_{B}[/tex], [tex]k = 9\times 10^{9}\,\frac{kg\cdot m^{3}}{s^{2}\cdot C^{2}}[/tex] and [tex]r = 0.29\,m[/tex], then the electric charge is:
[tex]-24\,J = -\frac{\left(9\times 10^{9}\,\frac{kg\cdot m^{3}}{s^{2}\cdot C^{2}} \right)\cdot (45\times 10^{-6}\,C+q_{B})\cdot q_{B}}{0.29\,m}[/tex]
[tex]-6.96 = -405000\cdot q_{B}-9\times 10^{9}\cdot q_{B}^{2}[/tex]
[tex]9\times 10^{9}\cdot q_{B}^{2}+405000\cdot q_{B} -6.96 = 0[/tex] (2)
Roots of the polynomial are found by Quadratic Formula:
[tex]q_{B,1} = 1.327\times 10^{-5}\,C[/tex], [tex]q_{B,2} \approx -5.827\times 10^{-5}\,C[/tex]
Only the first roots offer a solution that is physically reasonable. The charge of the negative one is 13.27 microcoulombs and the positive one has a charge of 58.27 microcoulombs.
While camping in a tent on a cold night, which would keep you warmer for a longer period of time. a 10 kg
bag of hot iron pellets or a 10 kg bag of hot water at the same temperature? Explain. PLEASE ANSWER
Answer:
a 10 kg bag of hot water at the same temperature
Explanation:
A 10kg bag of hot water at the same temperature will retain heat much better and keep the tent warmer at night compared to the iron pellet.
Water has a very large specific heat capacity. The specific heat capacity of water allows for it to retain heat better. It takes a larger amount of heat to warm water compared to iron which is a better conductor. In like manner, it takes more time for water to lose that amount of heat it has gained by the heating process. This is why it is a better choice to keep the room warmPlanet Earth is held in orbit by the sun's gravitational force pulling on the Earth.
Which one of the following statements are true about that gravitational force?
The sun does not have a gravitational force because it is made of gas.
The earth pulls with more force since it is less massive than the sun.
The sun and the earth pull on each other with equal and opposite forces.
The sun pulls with more force since the sun is more massive than the earth.
Answer:
The sun pulls with more force since the sun is more massive than the earth.
Explanation:
That your answer because the Earth is getting pulled by the gravitational pull from the Sun
The levels of organization are Cell, Tissue, Organs, ____________, and Organism. what goes in the blank?
Answer:
Organ system because multiple organs make up an organ system and multiple organ systems make up an organism
Each spring, a crevice in the cliff wall widens and deepens. What is the best explanation for how physical weathering causes the crevice to widen and deepen?
Winds deposit sand into the crevice.
Water freezes and expands in the crevice.
Snow melts and evaporates between the rocks in the crevice.
Air pollution in the area causes a reaction that widens the crevice.
Answer: water freezes and expands in the crevice
Explanation:
Answer:
Water freezes and expands in the crevice
Explanation:
How is the Moon thought to have formed
The most common complaint among patients about their doctors is the time spent waiting in the doctor's office. Patients claim that doctors overbook appointments. Doctors claim that a significant number of patients fail to show or are late for their appointments. Doctors also note that as medical professionals they must tend to anyone who has need of their service. The medical profession is also uncertain because doctors never know when an emergency will occur. Considering the economic concepts of scarcity and economic resources, why must doctors book as many patients as necessary during office hours?
A doctor has the time and resources to choose how many patients to treat
A doctor, by law, must treat every patient who shows up in a medical facility
A doctor must make as much money as possible during normal business hours
A doctor's time is scarce and must be used effectively to see the most patients
Answer: B- a doctor, by law, must treat every patient who shows up in a medical facility
Explanation:
A beaker with water resting on a scale weighs 40 N. A block
suspended on a hanging spring weighs 20 N. The spring scale
reads 15 N when a block is fully submerged in the water. What is
the reading of a scale on which the beaker with water rests, while
the block is submerged in the water after detached from the
hanging spring?
A. 25 N B. 60 N C. 55 N D. 45 N
Answer:
D. 45 N
Explanation:
The weight of the block is 20 N, when the block is fully immerged in water, it weighs 15 N. Hence the loss of weight = 20 N - 15 N = 5 N.
The loss of weight is as a result of the buoyant force. The buoyant force is the upward force exerted by a fluid when an object is fully or partially immersed in a fluid.
The buoyant force of 5 N acts in the upward direction, the weight of the beaker that would be read by the scale when the beaker is immersed in water = 40 N + 5 N = 45 N
the earth's moon has a gravitational field strength of about 1.6 n/kg near its surface. the moon has a mass of 7.35x10^22 kg. what is the radius of the moon? please show steps on how to do it please.
Answer:
1750km
Explanation:
A protein molecule in an electrophoresis gel has a negative charge. The exact charge depends on the pHpH of the solution, but 30 excess electrons is typical. What is the magnitude of the electric forceon a protein with this charge in a 1500 N/C electric field?
Answer:
The magnitude of the force = 7.2 × 10⁻¹⁵ C
Explanation:
The total quantization of charge q on an electron = n × e
where;
n = 30
e = 1.6 × 10⁻¹⁸ C
q = 30 × 1.6 × 10⁻¹⁸ C
q = 4.8 × 10⁻¹⁸ C
Now, the magnitude of the force is determined by using the formula:
F = qE
F = ( 4.8 × 10⁻¹⁸ C) ( 1500 N/C)
F = 7.2 × 10⁻¹⁵ C
how does a battery work?
Answer:
Essentials. A battery is a device that stores chemical energy and converts it to electrical energy. The chemical reactions in a battery involve the flow of electrons from one material (electrode) to another, through an external circuit. The flow of electrons provides an electric current that can be used to do work.
A cell phone weighing 80 grams is flying through the air at 15 m/s what is the kinetic energy
Answer:
[tex]9\:\mathrm{J}[/tex]
Explanation:
Kinetic energy is given by the following equation:
[tex]KE=\frac{1}{2}mv^2[/tex], where [tex]m[/tex] is mass in [tex]\mathrm{kg}[/tex] and [tex]v[/tex] is velocity in [tex]\mathrm{m/s}[/tex].
Since the cell phone's mass is given in grams, we need to convert this into kilograms:
[tex]80\:\mathrm{g}\cdot \frac{1\:\mathrm{kg}}{1000\:\mathrm{g}}=0.08\:\mathrm{kg}[/tex].
Therefore, the kinetic energy of the cell phone is:
[tex]KE=\frac{1}{2}\cdot 0.08\cdot 15^2=\fbox{$9\:\mathrm{J}$}[/tex].
a) A bus of mass 760 kg requires 120 m to reach certain velocity value Vf. Ignore friction and drag forces and assume the bus engine exerts a constant forward force F. When the bus is towing a 330-kg small car, how long distance needed to reach same Vf? b) If the Vf of the bus is 28 m/s, what is the tension in the tow cable between bus and small car?
Answer:
Given : A bus of mass 760 kg requires 120 m to reach certain velocity value Vf.
the bus engine exerts a constant forward force F.
To Find : When the bus is towing a 330-kg small car, how long distance needed to reach same Vf?
Solution:
V² - U² = 2aS
V = Vf
U = 0
S = 120 m
=> Vf² - 0 = 2a(120)
=> Vf² = 240a
m = 760 kg
Force = F
F = ma
=> F =760 a
=> a = F/760
Vf² = 240F/760
Case 2 :When the bus is towing a 330-kg small car,
m = 760 + 330 = 1090 kg
a = F/1090
Vf² = 2aS
=> 240F/760 = 2 (F/1090) S
=> S = 120 x 1090 /760
=> S = 172.1 m
172.1 m distance needed to reach same Vf
Explanation:
Two microwave signals of nearly equal wavelengths can gener- ate a beat frequency if both are directed onto the same microwave detector. In an experiment, the beat frequency is 100 MHz. One microwave generator is set to emit microwaves with a wavelength of 1.250 cm. If the second generator emits the longer wavelength, what is that wavelength
Answer:
the longer wavelength is 1.2552 cm
Explanation:
given that
beat frequency [tex]f_{b}[/tex] = 100 MHz = 100 × 10⁶ Hz
λ₁ = 1.250 cm = 0.0125 m
we know that beat frequency [tex]f_{b}[/tex] of two simultaneous frequencies f₁ and f₂ is expressed as;
[tex]f_{b}[/tex] = | f₁ - f₂ |
we know that microwave travels at a speed of light, so for any electromagnetic wave traveling at speed of light c with wavelength λ; frequency is;
f = c / λ
hence our beat frequency [tex]f_{b}[/tex] becomes
[tex]f_{b}[/tex] = c ( 1/λ₁ - 1/λ₂)
to find the longer wavelength, λ₂
[tex]f_{b}[/tex] = c ( 1/λ₁ - 1/λ₂)
divide both side by c
[tex]f_{b}[/tex] /c = ( 1/λ₁ - 1/λ₂)
1/λ₂ = 1/λ₁ - [tex]f_{b}[/tex] /c
λ₂ = [1/λ₁ - [tex]f_{b}[/tex] /c ]⁻¹
so we substitute in our values
we know that speed of light c = 3 × 10⁸
so
λ₂ = [ (1/0.0125) - (100 × 10⁶ /3 × 10⁸) ]⁻¹
λ₂ = [80 - 0.3333 ]⁻¹
λ₂ = [79.6667 ]⁻¹
λ₂ = 0.01255 m
λ₂ = 0.012552 × 100 cm
λ₂ = 1.2552 cm
Therefore, the longer wavelength is 1.2552 cm
In one type of Combustion reaction, _______ is combined with oxygen to create heat and light.
A) nitrogen
B) carbon
C) hydrogen
Answer:
carbon.
Explanation:
the reaction would then create c02 as a product