I need help! 20 points.

No system is completely closed off from its surroundings.

Which example represents a system that is almost completely closed?

a freezer with the door shut

a wood-burning fireplace

a cup of tea on a counter


a pot of simmering soup

These are just personal definitions of the following. They aren't official ones that may come from your textbook, but they are still accurate.

a. Friction is a force that acts against forces in contact with an object.

b. Sliding Friction is a force that acts against the forces making an object slide (e.g. the y component of the object's weight force if it's on an incline)

c. Static Friction is a force that acts on an object that is still/not moving.

d. Rolling Friction is the force making an object roll.

e. Air resistance is a frictional force that acts to slow down a falling object.

f. Terminal velocity is the maximum an object can reach while in free fall due to air resistance.

g. Gravity is a mutual attractive force in between two objects.

h. Weight is the mass of an object multiplied by the gravitational force (usually 9.81 for objects on earth). Weight is a force acting against the normal force keeping objects from phasing through each other.

i. Centripetal force is a force that acts on an object that is turning. This force pulls the object to the outside of the turning track.

j. Momentum is defined by mv (mass times velocity). Momentum is not a force, it is the idea that the motion of an object can depend on its mass and velocity.

I would check official dictionaries, just to make sure these definitions align with your textbook's.

"Scientific evidence for warming of the climate system is unequivocal."

Organisms such as diatoms, forams, and coral) can obey useful climate proxies. Other proxies involve ice cores climate, tree rings, and sediment cores. Chemical deputy records include isotope ratios, elemental examination, biomarkers, and biogenic silica.

Climate analyzers use every possible direct and indirect compilation to study the full history of Earth's climate, ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers appear that Earth's climate greets to changes in greenhouse gas levels.

So we can conclude that Climate change is most usually measured using the average surface temperature of the planet.

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In the given case it can be concluded that-  The two basic tenets of the special theory of relativity were that observers moving at constant speeds should be subject to the same physical rules and that the speed of light is constant for all observers.

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Torque is calculated using the formula =|r| |F|sin = | r | | F | sin, where |r| is the size of the lever arm, |F| is the size of the force vector, and is the angle formed between the two vectors.

Under ideal circumstances, M = F x r would be the equation for drive torque. In this instance, r denotes the length of a lever that is fastened to the axis of rotation and whose end is subject to a perpendicular force, F. The point of application, however, may alternatively be chosen at random.

The rotational rate (or "r") of an object is the amount by which a force acting on it rotates it. We'll refer to the force a "F" The moment arm, indicated by the letter "r," is the distance from the pivot point to the point at which the force acts.

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This electricity is then directed from the electric generator to electric outlets in homes

A power source that creates electricity through the use of giant magnets that are rotated to create a flow of electrons is called a generator. Generators use the principle of electromagnetic induction to convert mechanical energy (rotational energy of the magnets) into electrical energy.The electricity generated by the generator is then directed through electrical transmission lines to a substation, where it is transformed to a higher voltage level for long-distance transmission. Then it is distributed to homes and businesses through power lines and transformers.

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The truck exerts more force on the mosquito than the mosquito exerts on the truck is true during the collision.

What is the exerts?
Exerts is a term used to describe a passage or an extract taken from a larger piece of writing. Exerts are often used to showcase a specific part of a work and can be used to highlight the most important or influential passages. Exerts can be used to support or illustrate an argument, and can be used to provide evidence for a point that is being made. Exerts are often found in essays, scholarly articles, and other forms of writing, and are a useful tool for authors to draw attention to certain points or ideas.

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The value W' along inclined plane = (150 sin α ) N

W = m x g = 150 N --> based on case

W = weigth

m = massa

g = gravity acceleration

Fn = Normal force

Fn = m x g x cos α = W cos α = 150 N x cos α

W’ = m x g x sin α = W sin α = 150 N x sin α

Since the angle α is not known it will be still variable, so we could say that the W’ = (150 sin α ) N

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According to reports, the biggest meteorite with lunar origin weighs 19 g. If the meteorite placed on a scale whose spring constant is 83 N/m, 0.22 m is the compression of the spring.

We can use Hooke's Law to calculate the compression of the spring caused by the meteorite. Hooke's Law states that the force exerted on a spring is directly proportional to the spring's compression or extension.

= F

= k * x

where F is the force (in newtons), k is the spring constant (in N/m), and x is the compression (in meters).

Given the mass of the meteorite is 19 g and the spring constant is 83 N/m, the force exerted on the spring can be calculated as

= F

= (mass of the meteorite) * g

= (19 g) * (9.8 m/s^2)

The compression of the spring can be found by rearranging Hooke's Law and substituting in the force and spring constant

x = F/k

x = (19 * 9.8) / 83

x = 0.22 m

The compression of the spring caused by the meteorite is 0.22 m.

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When a single note is kept for a long time, it seems very soft to him. This is because he is standing at a point where the rarefactions of the sound wave from one speaker meet the compressions of the sound wave from the other speaker.

A longitudinal wave propagates by means of compressions and rarefactions. When a vibrating object motions forward, it shoves and compresses the air in a veneer of it building a region of high pressure. When a sound wave travels through a medium, say air, the particles of the medium disturb in the same fashion, i.e. compression and rarefaction. Compression is illustrated for the longitudinal waves in which the particles come nearer such that it is at high pressure.

Rarefaction is specified for the longitudinal waves in which the particles move apart such that it has low pressure.

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The temperature difference of  1 K on the Kelvin scale is equivalent to the temperature difference of (5/9)°F on the Fahrenheit scale.  Triple-point temperature of water is approximately 491 degrees Rankine.

The unit of scales on the Rankine scale is the same as those on the Fahrenheit scale. Hence, from the freezing point of water (0⁰C) to the boiling point of water(100⁰C) , Rankine scale is divided into 180 scales.

The absolute zero is zero degrees Rankine.  In Celsius scale, absolute zero is −273 °C.

A). A unit scale on the Kelvin scale is the same size as a unit scale in the Celsius scale. Hence,

ΔT 1 K = ΔT 1°C

The ratio of Celsius and Fahrenheit scale is 5/9, therefore:

K/F = C/F = 5/9

Hence,

ΔT 1 K = ΔT (5/9)°F

B) Triple-point temperature of water is approximately 0 °C. Since zero degrees Rankine is equivalent to  −273 °C, hence:

0 °C = 0 - (9/5)(-273) = 491 degrees Rankine.

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The minimum speed of the car at the top of the loop for it to stay on track be 1.57 m/s.

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The ball accelerates at a constant rate as it moves down the slope because of the constant gravitational force acting on it in a major portion and the rolling tangential force on the object is acting in the smaller form.

Rolling motion of any object occurs when the object starts sliding in a different methods from the other objects such as when the objects starts to roll from the ramp or any other sloppy surface and it rolls down due to the gravitational force and with many other forces such as the rolling tangential force. many forces are acting on the object at the same moment and we are just seeing the gravitational force which is playing a major portion. Hence by this information we can consider that the ball accelerates at a constant rate as it moves down the slope because of the constant gravitational force acting on it in a major portion and the rolling tangential force on the object is acting in the smaller form.

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An explanation for the apparent increase in the rate at which the universe is expanding is dark energy. The correct option is b.

A hypothesized energy known as "dark energy" acts in opposition to gravity by exerting a repellent, negative pressure. It has been proposed to explain the observable characteristics of far-off type Ia supernovae, which reveal the universe is expanding at a faster rate than usual.

We would first need to locate dark energy before scientists could even consider whether it could be possible to use it as a source of electricity.

Therefore, the correct option is b. dark energy.

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Answer:

The total amount of energy necessary to carry out this process is 22600 joules (J).

Explanation:

This is because the heat of vaporization (the energy required to change the state of water from liquid to gas) of water is 2260 J/g. Since 10.0 g of water is being heated, the total amount of energy needed is 10.0 g * 2260 J/g = 22600 J.

To find the average speed of the cyclist, we need to divide the distance traveled by the time it took to travel that distance. So we would divide 100 meters by 40 seconds, which gives us 2.5 meters per second. This is the average speed of the cyclist.

Answer:

The Average Speed is 2.5metres per second

Explanation:

Using Distance,Time,Speed Triangle,

[tex]S = \frac{D}{T}[/tex]

[tex]S = \frac{100}{40}\\[/tex]

[tex]S = 2.5[/tex]

Hence ,  the average speed is 2.5m/s

Correct option is A, A heavy truck and a small truck roll down a hill. Neglecting friction, at the bottom of the hill the heavy truck has greater acceleration.

Momentum and mass are directly proportional in direction. This is so because mass times velocity make up the equation for momentum. Another way to express this is as p = m*v, where p stands for momentum, m for mass, and v for velocity. As a result, momentum doubles if mass is increased by a factor of two but velocity remains constant.

p = m v . The equation demonstrates that momentum is directly related to an object's mass (m) and velocity (v). As a result, an object's momentum increases with increasing mass or velocity. The momentum of a large, swift object is larger than that of a small, slower object.

The definition of momentum is "mass in motion." Since every item has mass, if it is moving, it must have momentum because its mass is in motion. The amount of motion and the speed of the motion are the two factors that determine how much momentum an item possesses.

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You and your friend will have the same potential energy at the top of the tower because gravitational potential only depends on height and not on how an object got there.

The power that a substance retains as a result of its position in relation to other things, internal pressures, electric charge, or other substances is known as potential energy in physics. Potential energy is a form of energy that is stored but is dependent on the interactions of different system components.

A steel ball has more potential energy if it is raised above the ground as opposed to dropping to it. The energy that is present in everything that is raised from rest and has the potential to be released at a later time is known as potential energy.

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The formulas F(A)×R(A) = F(B)×R(B) should be used to determine the distance of item B from the fulcrum such that it balances object A. where F is the object's force and R is the object's distance from the fulcrum.

The push or pull that causes a massed body to change its speed is the definition of force. An agent with the ability to change a body's rest or moving condition is known as an external force. It has a magnitude as well as direction.

Forces are created by the interactions between two (or more) objects. There is a similar but opposing force acting on each individual on the other. External forces are what cause the item to move.

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The quantum numbers of the 2 states involved in the transition that emits these photons of energy 1.89 eV of hydrogen is n=3 to n=2

The hydrogen atom is the simplest atom in which an electron moves in the spherically symmetric Coulomb potential of the proton. The total energy of an atom in the center of the mass system can only have discrete values for the stationary states described by the quantum numbers.

Energy of the emitted photon, ΔE=1.89eV. The total energy of a hydrogen atom is given as, En=−13.6/n^2eV, Here, n is the principal quantum number.

An electron absorbs or emits radiation in the form of discrete energy, which equals the difference in energies of the final and initial state. Mathematically, ΔE=Ef−Ei. Here, Ef  is the energy of the final state and Ei  is the energy of the initial state.The difference in energy when an electron makes transition from n=3 to n=2. ΔE3→2= E3−E2=(−1.51eV)−(−3.4eV)= 1.89eV.

Since, ΔE=ΔE3→2. Therefore, the electron makes a transition from n=3 to n=2.

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The velocity of the bike is 2.57 m/s. Then the kinetic energy of the 44 kg mass is 145.3 J.

Kinetic energy of an object is generated by virtue of its motion. Kinetic energy is related to the mass and velocity of the object by the expression written below:

Ke = 1/2 m v²

Given the distance travelled = 1.70 km = 1700 m

time taken = 11 min = 660 s

then velocity = distance/ time = 1700 /660 = 2.57 m/s

Total mass = 44 kg

Ke = 1/2 44 Kg × (2.57)² = 145.3 J

Therefore, the kinetic energy of Shawn and his bike is 145.3 J

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The distance between the Naval Navigator and the sunken cargo was found to be 2175 m by using sonar with 120kHz frequency and a wavelength of 3mm.

Sonar is largely used by NOAA scientists to create nautical charts, find underwater navigational hazards, find and map things on the bottom like shipwrecks, and map the actual seafloor. Sonar comes in active and passive varieties.

Speed of sound in water  =1450m/s

Time lag between transmission and reception of Sonar waves =3 s

sound waves travel a distance is twice the distance between the navigator and cargo (2S) in this time lag.

Time taken for the sound to reach the submarine  = 1/2 ×3 = 1.5s

Distance between the Navigator and the sunken cargo, S=1450×1.5s =2175m.

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The height of the hill can be calculated using the formula PE = mgh, where m is the mass, g is the acceleration due to gravity (9.8 m/s2), and h is the height of the hill. So, solving for h, we get h = PE/mg = 1000 J/ (60.0 kg*9.8 m/s2) = 10.2 m.

Therefore, the height of the hill is 10.2 m.  The potential energy of an object is the energy it possesses due to its position or state. As the object moves, its potential energy can be converted into kinetic energy, or the energy it has due to its motion. In this case, the rollerblader is on top of the hill, so it has potential energy due to the height of the hill.  

The formula for potential energy is PE = mgh, which means that the potential energy is equal to the mass multiplied by the acceleration due to gravity multiplied by the height. In this case, the mass is known to be 60.0 kg, and the potential energy is known to be 1000 J. By using the formula and substituting in the known values, the height of the hill can be calculated.

The height of the hill is determined to be 10.2 m, which is relatively small. This means that the hill is not too steep, and the rollerblader would not have to use a lot of energy to go down it.

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Sometimes in phase and sometimes out of phase.The voltage across the resistor and generator will depend on the phase difference between the current and voltage in the circuit.

The voltage across the resistor and generator will depend on the phase difference between the current and voltage in the circuit. If the phase difference is 0°, then the voltage across the resistor and generator will be in phase. If the phase difference is 180°, then the voltage across the resistor and generator will be out of phase. In any other scenario, the voltage across the resistor and generator will be somewhere in between in phase and out of phase.

Sometimes in phase and sometimes out of phase.

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Answer:

Initial velocity of the van is 4.95m/s

Explanation:

Acceleration is found using the following formula:
[tex]a=\frac{v-u}{t}[/tex]

where:

a is acceleration ( in meters per second squared)
v is final velocity ( in meters per second)
u is initial velocity ( in meters per second)
t is time ( in seconds)

We know that:
[tex]a = 2.15m/s^{2}[/tex]

[tex]v = 20m/s[/tex]

[tex]t=7s[/tex]

Therefore, we can find the initial velocity by shifting around some values and making [tex]u[/tex] the subject within the acceleration formula by multiplying both sides by [tex]t[/tex]:
[tex]a[/tex] × [tex]t=v-u[/tex]

Followed by:
[tex]u = v-at[/tex]

Now we can substitute in the values we have:
[tex]u = 20-(2.15[/tex] × [tex]7)[/tex]
[tex]u = 20 - 15.05[/tex]

[tex]u=4.95m/s[/tex]

The mass of the electrons associated with the neutral atoms must also be taken into account.

Part A

21284Po → 20880Pb + 4He

Part B

E = 13.9 MeV

Part C

23994Pu → 23592U + 4He

Part D

E = 16.2 MeV

For Part A and C, the nuclear equations of the decay process are determined by subtracting the mass number of the products from the mass number of the reactants. The mass number of the reactants is the sum of the mass number of the parent nucleus and 4 for the alpha particle.

For Part B and D, the energy released in the reaction is determined by subtracting the mass of the products from the mass of the reactants and converting to energy using the equation E = mc2. The masses of the reactants and products are found using the atomic masses listed in the periodic table. The mass of the electrons associated with the neutral atoms must also be taken into account.

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Potential energy is the power that a thing possesses as a result of where it is in relation to other objects.

The earth can pull you down through the force of gravity while doing work in the process, being at the top of a stairwell gives you more potential energy than standing at the bottom.

Two magnets have more potential energy when they are held apart than when they are near to one another. They will migrate near each other and begin working if you let them go.

The force acting on the two objects affects the potential energy formula. P.E. = mgh, where m is the mass in kilograms and g is the acceleration due to gravity, is the formula for gravitational force.

Therefore, Potential energy is the power that a thing possesses as a result of where it is in relation to other objects.

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Answer:

2.58 m/s

Explanation:

To determine the theoretical speed at which the golf ball must have left the floor, you can use the principle of conservation of energy, which states that the total energy in a closed system remains constant. In this case, we can use the fact that the ball's potential energy changes as it rises and falls.

First, we know that the efficiency of the ball is 61.0%, so we can assume that 39% of the energy is lost as heat, sound, etc. We can calculate the initial kinetic energy (Ei) of the ball as:

Ei = Efficiency * (Initial Potential energy - Final Potential energy)

Ei = 0.61 * (0.444 - 0.271) = 0.119J

Now, we can use this value to calculate the velocity (Vi) of the ball as it left the floor, by using the equation of kinetic energy:

Ei = 0.5 * m * Vi^2

Where:

m = mass of the ball = 0.0453 kg

Vi = velocity of the ball when it left the floor

By substituting the values in the equation we get:

0.119 = 0.5 * 0.0453 * Vi^2

Solving for Vi:

Vi = sqrt(0.119 / (0.5 * 0.0453))

Vi ≈ 2.58 m/s

So, the theoretical speed with which the ball must have left the floor is approximately 2.58 m/s

Keep in mind that this is a theoretical speed and there may be a variance with real-world observations.

When a loose brick is resting on a wall, it has potential energy. When the brick is pushed off the wall and is falling down, the amount of potential energy is decreasing while the amount of kinetic energy is increasing.

Kinetic energy is motion––of waves, electrons, atoms, molecules, substances, and objects. Potential energy is stored energy and the energy of position––gravitational energy. There are several forms of potential energy.

Conservation of energy is not saving energy. The law of conservation of energy says that energy is neither created nor destroyed. When we use energy, it doesn’t disappear. We change it from one form of energy into another.

A car engine burns gasoline, converting the chemical energy in gasoline into mechanical energy. Solar cells change radiant energy into electrical energy. Energy changes form, but the total amount of energy in the universe stays the same.

Energy efficiency is the amount of useful energy you get from a system. A perfect, energy-efficient machine would change all the energy put in it into useful work—an impossible dream. Converting one form of energy into another form always involves a loss of usable energy.

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Answer:  1580 J

Explanation:

Energy is in the form of gravitational potential energy. (GPE)

GPE = mgh , where m is the mass of the block, h is the height and g is the gravitational constant of 9.81 ms-2.

Hence,

Total energy = mass x gravitational constant x height

                      = Weight x height (since W = mg)

                      = 79 x 20 J

                      = 1580 J

The momentum of the rock by the student is 0.500kgm/s.

Momentum -

momentum is the result of a particle's mass and velocity. Being a vector quantity, momentum possesses both magnitude and direction. According to Isaac Newton's second equation of motion, the force applied on a particle is equal to the time rate of change of momentum. Check out Newton's laws of motion.

Momentum can be viewed as a body's "power" while it is moving, or the amount of force it can exert on another body. For instance, a baseball (small mass) thrown quickly can have the same momentum as a bowling ball (big mass) going extremely slowly (low velocity) (high velocity).

Momentum = Mass × Velocity

Momentum of rock = 0.500 × 1

= 0.500kgm/s

Momentum of Boy = 45 × 0 [As boy is at rest so, he has 0 momentum]

Momentum of boy = 0

Total Momentum = Momentum of rock + Momentum of boy

= 0.500 + 0

= 0.500 kgm/s

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