A star of spectral type O lives approximately how long on the main sequence? A) 1,000 years. B) 10,000 years. C) 10 million years. D) 100 million years

Answer:

The coefficient of cubical expansion of a solid is defined as the increase in volume of a solid per unit volume per degree Celsius rise in temperature. It is denoted by the symbol α.

Mathematically, we can express the coefficient of cubical expansion as:

α = (1/V) x (dV/dT)

where V is the volume of the solid and dV/dT is the rate of change of volume with respect to temperature.

The variation of density with temperature can be expressed using the coefficient of cubical expansion as follows:

ρ = m/V, where ρ is the density of the solid and m is its mass.

Differentiating this expression with respect to temperature, we get:

dρ/dT = (1/V) x (dm/dT) - (m/V^2) x (dV/dT)

Using the relationship between the coefficient of cubical expansion and the rate of change of volume with respect to temperature, we can substitute (dV/dT) = αV into the above expression to obtain:

dρ/dT = (1/V) x (dm/dT) - αρ

This equation shows that the variation of density with temperature is directly proportional to the coefficient of cubical expansion of the solid.

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An existing surface low-pressure system would probably stay stagnant or diminish due to the lack of support from upper-level dynamics if there was no divergence or convergence in the upper troposphere.

On the other hand, sea-level pressures rise in areas of convergence in the upper atmosphere. Surface high-pressure systems are often characterized by calm, largely clear weather due to the ensuing low-level divergence and sinking air.

The pressure systems traveling along the surface are enhanced or suppressed by this convergence and divergence. The air density above, for instance, will decrease when there is a region of diverging air in the upper troposphere.

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Kinetic energy just before it hits the ground will be equal to mgh by law of conservation of energy.

An apple hanging from a tree contains potential energy due to its elevated position. whenever an apple falls from a tree. The fruit contains kinetic energy, which is why it is falling. As a result, when the apple starts falling, the potential energy that was previously held in it at its raised position is converted into kinetic energy.

The height is always the vertical distance between the starting point and the lowest point of fall, not necessarily the entire distance the body may go. Almost all mechanical processes include the exchange of work and kinetic and potential energy.

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Each rocket will need to provide a steady force of 6.98 N to accelerate the satellite to 25 rpm in 6.5 minutes.

We can use the following equation to solve this problem,

ω = (1/2) α t^2

where,

ω = final angular velocity (25 rpm)

α = angular acceleration

t = time taken to reach final velocity (6.5 minutes = 390 seconds)

Since the satellite starts from rest, the initial angular velocity is 0. Thus, rearranging the equation,

α = (2ω) / t^2

α = (2 x 25 rpm x 2π rad/rpm) / (390 s)^2

α = 0.0008727 rad/s^2

Each rocket will need to provide a torque to generate this angular acceleration. The required torque is given by,

τ = Iα

where,

τ = torque required

I = moment of inertia of the satellite

The moment of inertia of a solid sphere is given by,

I = (2/5) mr^2

where, m = mass of the satellite and r = radius of the satellite.

Let's assume the satellite has a mass of 1000 kg and a radius of 2 meters.

I = (2/5) x 1000 kg x (2 m)^2

I = 8000 kg m^2

Therefore, the torque required by each rocket is,

τ = Iα

τ = 8000 kg m^2 x 0.0008727 rad/s^2

τ = 6.98 Nm

Since there are two rockets, each rocket will need to provide half of this torque, or,

F = τ / r

where, F = force required by each rocket and r = distance from the center of the satellite to the rocket (let's assume this is 1 meter)

F = 6.98 Nm / 1 m

F = 6.98 N

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When an electric dipole oscillates along the x-axis, it creates an electromagnetic wave with an electric field that oscillates perpendicular to the direction of propagation of the wave.

Electric dipoles are widely used in various applications, including antennas, sensors, and electronic devices.  The separation between the charges is known as the dipole moment and is denoted by the symbol "p". The concept of electric dipole is also essential in understanding many fundamental concepts in electromagnetism, such as electric fields, electric potentials, and electric forces.

The electric dipole moment plays an important role in many physical phenomena, such as the interaction between molecules in a polar solvent, the electric field near a polar molecule, and the interaction between charges in an external electric field. In the presence of an external electric field, an electric dipole experiences a torque that aligns the dipole moment with the electric field direction. This phenomenon is known as the orientational polarization of the dipole.

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Complete Question:-

An electromagnetic wave is created when an electric dipole with its centre located at the origin of a Cartesian coordinate system oscillates along the x axis. At a position on the z axis far from the origin, the polarization of the wave is the orientation of the electric field, which is parallel to the x axis.

The average force exerted by the oxygen molecule on one of the walls of the container is 8.5 x 10^-20 N. This value is calculated using the formula   [tex]F = (2mv^2)/(Δt * d) where Δt = 5.0 x 10^-4 s[/tex] and d = 0.10 m.

When an oxygen molecule bounces back and forth between opposite sides of a cubical vessel, it exerts a force on each of the walls it strikes. To calculate the average force exerted by the molecule on one of the walls, we use the formula [tex]F = (2mv^2)/(Δt * d)[/tex], where m is the mass of the molecule, v is its velocity, Δt is the time it takes for the molecule to travel from one wall to the opposite wall and back, and d is the distance between the two opposite walls.

Substituting the given values, we get [tex]F = 8.5 x 10^-20 N[/tex]. This is a very small force, which is expected for a single oxygen molecule in a container. However, for a large number of molecules, the total force exerted on the walls of the container can be significant, leading to the pressure inside the container. This principle is used in many industrial and everyday applications, such as gas storage, refrigeration, and air conditioning.

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The strength of the electric field between two parallel conducting plates separated by 1.50 cm and having a potential difference (voltage) between them of 1.25 x 104 V is 8.33 x 10⁵ V/m

What is an electric field?An electric field is an area in which an electric charge undergoes a force. It is usually produced by electric charges or by time-varying magnetic fields. An electric field is a vector field with a magnitude and direction that affects the motion of charged objects.

The formula for electric field strength is given by E = V/d, where,E is the electric field strength, V is the potential difference between the two parallel conducting plates, d is the distance between the two parallel conducting plates.

Given,V = 1.25 x 104 Vd = 1.50 cm = 0.015 mE = ?

Using the formula above, we can substitute the given values and calculate:

E = V/d = (1.25 x 104 V) / (0.015 m) = 833,333.33 V/m or 8.33 x 10⁵ V/m . The strength of the electric field is 8.33 x 10⁵ V/m

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The H-R diagram is the most important graph in astronomy. One of the reasons that this graph is so powerful is the number of different kinds of data it shows. Most graphs show two types of data. The H-R diagram shows seven.

The seven types of information about stars that appear on the H-R diagram are listed below:

1. Color: Color is the key factor that allows us to compare stars in the H-R diagram.

2. Temperature: Temperature is the physical quantity that determines the star's color, and it can be read off the H-R diagram.

3. Absolute magnitude: The actual brightness of a star is referred to as its absolute magnitude, which can be measured by astronomers.

4. Luminosity: A star's luminosity is the amount of energy it radiates per unit time, which can also be measured by astronomers.

5. Spectral type: The H-R diagram includes the spectral type of the star, which tells us what kind of light the star emits.

6. Surface gravity: The force that holds an object on the surface of a star is referred to as surface gravity.

7. Radius: A star's size is represented by its radius, which can be determined from the H-R diagram.

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The car would have been moving too fast for a safe stop and would have been moving at a speed even higher if it could have produced a skid mark of 65 mph with a friction coefficient of 0.25.

A skid mark is measured from the beginning of one, which may start out light if two tyres lock and gradually darken as more tyres lock.

Just dividing the vertical load by the horizontal force yields the coefficient of friction. For each section, the high, low, and average SN values are presented. The test speed has an impact on SN results; the slower the speed, the higher the SN.

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a) Megan's average speed is 12.5 meters per second.

b) The forward force on the bike becomes greater than the backward force on the bike.

As according to Newton's Third Law of Motion, every action must have an equal and opposite reaction. This means that when one object exerts a force on a second object, The second object enforces an equal magnitude and opposite direction force on the first object.

a) Megan's average speed can be calculated by dividing the total distance by the time taken:

Average speed = Total distance / Time taken

Here, the total distance covered by Megan is 400 m and the time taken is 32 seconds.

Average speed = 400 m / 32 sec = 12.5 m/s

When Megan is travelling at a constant speed, the forward force on the bike must be equal and opposite to the backward force on the bike, as per Newton's Third Law of Motion. Therefore, the forward force and backward force on the bike are equal.

b) When Megan crouches down on the handles to be more streamlined, the air resistance on the bike reduces. This leads to a reduction in the backward force acting on the bike, while the forward force remains the same. Therefore, the forward force on the bike becomes greater than the backward force on the bike.

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Petroleum is a widely used fuel source for transportation due to several reasons, including its high energy density, clean-burning properties, and liquid state.

Firstly, petroleum has a high energy density, which means that a small amount of petroleum can generate a large amount of energy. This is particularly important for transportation because it allows for a greater range or distance to be covered per unit of fuel, making it more efficient and cost-effective.

Secondly, petroleum is a clean-burning fuel, which means that it produces relatively fewer emissions and pollutants when it is burned compared to other fossil fuels like coal. This is important for environmental reasons, as reducing emissions can help to improve air quality and mitigate climate change.

Lastly, petroleum's liquid state makes it easy to transport and store, which is crucial for fueling vehicles. Liquids can be easily transported through pipelines or in tanks, and they can be easily dispensed at fuel stations. In addition, petroleum can be stored for long periods of time without deteriorating, which makes it an ideal fuel source for transportation.

In conclusion, petroleum is a convenient fuel source for transportation due to its high energy density, clean-burning properties, and liquid state. However, it is important to note that the use of petroleum has environmental impacts, and efforts are being made to transition to more sustainable and cleaner fuel sources.

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The initial similarity between the surface of Mercury and the Moon is primarily due to the existence of numerous impact craters caused by meteoroid and asteroid impacts.

An initial glance at the surface of Mercury indicates that it is somewhat similar to the surface of the Moon. This initial similarity is primarily due to the existence of impact craters, which are formed when a meteoroid or asteroid collides with the surface. Both the Moon and Mercury lack significant atmospheres and have solid, rocky surfaces that are geologically inactive, which means that craters are not erased by erosion or tectonic processes. The craters on both surfaces are also similar in appearance, with raised rims, flat floors, and central peaks. Additionally, both surfaces have extensive plains that were formed by volcanic activity, although the plains on Mercury are thought to be younger and more extensive than those on the Moon. Overall, the similarity between the surfaces of Mercury and the Moon is primarily due to their shared lack of geological activity and the prevalence of impact craters.

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In the wave, the particles of the medium are closer together in B. compressions.

Particles in a compressional wave compress and expand in the direction of wave propagation. In a compressional wave, when a force is exerted on one end of the chain of particles, it is transferred from one particle to the next, resulting in a disturbance in the medium that spreads outward. As a result, compressions and rarefactions travel through the medium, causing the particles to be either close together or far apart.

In a compressional wave, the particles in the medium vibrate parallel to the direction of wave propagation. This is due to the fact that the direction of particle movement in a compressional wave is in the same direction as the wave's motion. The particles in the medium are closer together in compressions, whereas they are further apart in rarefactions. The reason for this is that the particles in a medium are pushed together by the wave's pressure and then pushed apart as the wave continues. Therefore, the correct option is B.

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The work done by gravity on the block is 346.4 Joules.

The work done by gravity on an object is given by the formula,

W = Fd cos(theta)

where, W = work done, F = force applied, d = distance moved in the direction of the force, theta = angle between the force and the direction of motion. In this case, the force applied by gravity is the weight of the block, which is given by,

F = mg

where, m = mass of the block and g = acceleration due to gravity (9.8 m/s^2).

Substituting the given values,

F = 80 N

m = F/g = 80 N / 9.8 m/s^2 = 8.16 kg

The angle of the incline is 30 degrees, which means the angle between the force of gravity and the direction of motion is also 30 degrees. The distance moved by the block in the direction of the force is the length of the incline, which is given as 5m.

Therefore, the work done by gravity on the block is,

W = Fd cos(theta) = (80 N) x (5 m) x cos(30) = 346.4 J

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The magnetic force experienced by the particle when it enters a magnetic field of 2.2 T is given by:

F = qVBsinθ

where q is the charge of the particle, V is its velocity, B is the magnetic field, and θ is the angle between the velocity vector and the magnetic field vector. Since the angle is not given, we can assume it to be 90 degrees. So, sinθ = 1. Hence, the formula reduces to:

F = qVB

Now, we need to find the radius of the circular path that the particle traverses. The magnetic force provides the necessary centripetal force for circular motion.

Hence, we can equate the two forces as follows:

F = mv^2/r

where m is the mass of the particle and v is its velocity. Since the velocity of the particle is not given, we can assume it to be constant.

Hence, we can combine the two formulas as follows:qVB = mv^2/rSolving for r, we get r = mv/qBSubstituting the given values, we get:

r = (1.6 × 10^-19 C)(5 × 10^7 m/s)/(1.6 × 10^-31 kg)(2.2 T) = 0.665 m

Therefore, the radius of the circular path that the particle traverses are 0.665 meters.

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When a wool sock is dragged across a rug, there is a buildup of static electricity on the wool sock. The type of particle transferred between the rug and the sock to cause this static is an electron.

Static electricity is the electrical charges generated by electric charges that are not moving. In an electrically neutral atom or molecule, electrons and protons exist in equal numbers. A loss or gain of electrons results in a net electrical charge, and static electricity is generated when there is a charge buildup in an insulator.

The generation of electric charge depends on the nature of the materials, their humidity, and their temperatures. Rubber, plastic, and silk, for example, are excellent insulators that accumulate static electricity. Static electricity may result from the rubbing of insulators together or from an imbalance in the transfer of electrons between insulators. Electrons are transferred from the rug to the wool sock when a wool sock is dragged across a rug.

As a result, the wool sock has a static electrical charge.

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The outer Jovian planets are larger and mostly gaseous because they formed beyond the frost line, where water and methane condensed into large icy planetesimals that attracted the abundant light gases.

The outer planets are composed mainly of hydrogen and helium, which are the most abundant elements in the universe. These elements were able to condense into solid form beyond the frost line, where the temperature was low enough for them to freeze. The solid cores of the outer planets were able to attract and hold onto the abundant light gases, which formed the thick atmospheres of the outer planets.

In contrast, the inner terrestrial planets are smaller and denser because they formed inside the frost line, where the temperature was too high for hydrogen and helium to condense into solid form. Instead, the inner planets are composed mainly of rock and metal, which are denser than hydrogen and helium and were able to condense into solid form inside the frost line.

The Jovian planets are the outer planets of our solar system: Jupiter, Saturn, Uranus, and Neptune. These planets are also called “gas giants” or “giant planets” because they are much larger than the inner, rocky planets and are composed mainly of hydrogen and helium, which are the most abundant elements in the universe. The Jovian planets are named after their mythological namesake Jupiter, which is also known as Jove.

The Jovian planets have several characteristics in common, including their large size, low density, and thick atmospheres. They also have many moons and are surrounded by rings. The Jovian planets are located beyond the asteroid belt, which is the region of the solar system between Mars and Jupiter.

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My diagnosis for the left knee is that the patient likely has a torn or injured MCL. The sonogram showed thickening and irregularity of the MCL, indicating an injury.

This data means that there is damage to the MCL, which could lead to instability of the knee joint and ongoing pain and swelling.

When performing an ultrasound examination of the knee, the sonographer places the transducer on the skin over the area of interest, in this case, the medial aspect of the knee joint. The transducer sends out high-frequency sound waves that travel through the skin and soft tissues of the knee. When these sound waves encounter a boundary between tissues of different densities, some of the waves are reflected back to the transducer, while others are transmitted further into the body.

The reflected sound waves are detected by the transducer, which converts them into electrical signals that are processed by a computer to create an image of the knee. The image shows the different structures within the knee joint, including the MCL.

To diagnose an injury to the MCL, the sonographer will look for changes in the appearance of the ligament on the sonogram. The MCL appears as a hyperechoic band of tissue that extends from the femur to the tibia. If the MCL is torn or injured, it may appear thicker or thinner than normal or have an irregular shape.

In conclusion, my diagnosis for the left knee is that the patient likely has a torn or injured MCL. The sonogram showed thickening and irregularity of the MCL, indicating an injury.

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When the first bulb burns out, the power dissipated by each remaining bulb increases by a factor of approximately 1.0403.

Step 1: Determine the initial voltage across each bulb.

In the initial situation, there are 50 bulbs connected in series and the total voltage across them is 120 V. The voltage across each bulb can be calculated by dividing the total voltage by the number of bulbs.

Initial voltage across each bulb = Total voltage / Number of bulbs = 120 V / 50 = 2.4 V

Step 2: Determine the new voltage across each bulb when the first bulb burns out.

When the first bulb burns out, its special fuse creates a connection around it. Now, there are 49 bulbs in the circuit with the same total voltage of 120 V.

New voltage across each bulb = Total voltage / New number of bulbs = 120 V / 49 ≈ 2.449 V

Step 3: Calculate the power dissipation factor.

The power dissipated in each bulb is proportional to the square of the voltage across it (P = V^2/R, where R is constant). To find the factor by which the power dissipated increases, we will take the ratio of the new power to the initial power.

Power dissipation factor = (New voltage / Initial voltage)^2 = (2.449 V / 2.4 V)^2 ≈ 1.0403

When the first bulb burns out, the power dissipated by each remaining bulb increases by a factor of approximately 1.0403.

Note: The question is incomplete. The complete question probably is:  A string of holiday lights can be wired in series, but all the bulbs go out if one burns out because that breaks the circuit. Most lights today are wired in series, but each bulb has a special fuse that short- circuits the bulb—making a connection around it—if it burns out, thus keeping the other lights on. Suppose a string of 50 lights is connected in this way and plugged into a 120 V outlet. By what factor does the power dissipated by each remaining bulb increase when the first bulb burns out?

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a) The threshold frequency of a metal is the lowest frequency of electromagnetic radiation required to release electrons from a metal's surface in the photoelectric effect.

b) The given graph depicts the relationship between the frequency of incident electromagnetic radiation and the kinetic energy of released electrons for a specific metal.

ii. The slope of the graph, which represents Planck's constant, h, can be used to calculate the work function of the metal. The job function is provided by:

Work function = h x frequency threshold

The threshold frequency is 5.0 x 1014 Hz, according to the graph. The Planck constant is 6.626 x 10-34 J s. When these values are substituted into the preceding equation, the following results are obtained:

6.626 x 10-34 J s x 5.0 x 1014 Hz = 3.313 x 10-19 J.

ii) This metal's work function is 3.313 x 10-19 J.

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a) The threshold frequency of a metal is the lowest frequency of electromagnetic radiation required to release electrons from a metal's surface in the photoelectric effect.

b) The given graph depicts the relationship between the frequency of incident electromagnetic radiation and the kinetic energy of released electrons for a specific metal.

ii. The slope of the graph, which represents Planck's constant, h, can be used to calculate the work function of the metal. The job function is provided by:

Work function = h x frequency threshold

The threshold frequency is 5.0 x 10¹⁴ Hz, according to the graph. The Planck constant is 6.626 x 10⁻³⁴ J s. When these values are substituted into the preceding equation, the following results are obtained:

6.626 x 10⁻³⁴ J s x 5.0 x 10¹⁴ Hz = 3.313 x 10⁻¹⁹ J.

ii) This metal's work function is 3.313 x 10⁻¹⁹ J.

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Answer:

a) A photon with energy greater than or equal to the work function of the metal will cause photoemission.

From the given data, the work function of the metal is 1.7 eV. Therefore, photons with energies of 2.0 eV and 4.0 eV will cause photoemission, but the photon with an energy of 1.0 eV will not.

b) The maximum kinetic energy (KEmax) of a liberated electron is given by:

KEmax = E(photon) - work function

where E(photon) is the energy of the incident photon.

For the photon with an energy of 2.0 eV:

KEmax = 2.0 eV - 1.7 eV

KEmax = 0.3 eV

In joules:

KEmax = (0.3 eV)(1.602 x 10^-19 J/eV)

KEmax = 4.81 x 10^-20 J

For the photon with an energy of 4.0 eV:

KEmax = 4.0 eV - 1.7 eV

KEmax = 2.3 eV

In joules:

KEmax = (2.3 eV)(1.602 x 10^-19 J/eV)

KEmax = 3.69 x 10^-19 J

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A magnetic field created by the electric current causes the compass needle to move. Option D is the correct answer.

When an electric current flows through a wire, it creates a magnetic field around the wire. The direction of the magnetic field is determined by the direction of the current. When a compass is placed next to the wire, the magnetic field created by the current causes the compass needle to move.

In a simple circuit made from a battery, a light bulb, and a wire, the electric current flows from the battery, through the wire, and through the light bulb, and then back to the battery. This creates a magnetic field around the wire, which can cause the compass needle to move when it is placed next to the wire. Hence, option D is correct choice.

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The primary rationale for the technician's precautions about radiation exposure is to protect their health. Ionizing radiation can cause damage to the body's cells and the risk increases with increased exposure.

The technician wants to minimize their exposure to radiation to reduce their risk of developing cancer or any other health issues that may arise from over exposure to radiation. Even though the levels of radiation used in contemporary radiologic imaging are relatively low, it is important for the technician to take precautions to protect their health.

This includes standing behind protective shields, wearing protective clothing and avoiding long-term exposure to the radiation source.

Additionally, the technician should ensure that any equipment they use is regularly tested to ensure it is working properly and is providing the lowest possible dose of radiation. By following these safety precautions, the technician can ensure their safety and reduce their long-term risk of developing any health issues from radiation exposure.

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The speed of the joined cars after the collision is most likely less than the speed of car b before the collision.

This is due to the principle of conservation of momentum, which states that the total momentum of a closed system remains constant if no external forces act on it. In this case, the system is the two toy cars, and the collision is a closed system because no external forces are acting on the cars.

Before the collision, car b has a certain momentum, and car a has zero momentum since it is at rest. After the collision, the two cars stick together and move in the same direction as car b before the collision. The total momentum of the system remains constant, but now it is shared between the two cars. Since the total mass of the system has increased, the speed of the joined cars after the collision will be less than the speed of car b before the collision.

To calculate the exact speed of the joined cars after the collision, we would need to know the masses and initial velocities of the two cars. However, we can say with certainty that the speed will be less than the speed of car b before the collision due to the conservation of momentum.

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The width of the dips in the star's brightness would be different for planets at different distances from the star because the transit depth, which determines the dip width, depends on the planet's size relative to the star.

When a planet passes in front of its star, it blocks a portion of the star's light, causing a temporary decrease in brightness that can be observed from Earth. If the planet is small compared to the star, the dip in brightness will be small, and if the planet is large compared to the star, the dip will be larger. Therefore, the width of the dips in the star's brightness would be different for planets at different distances from the star because the transit depth depends on the planet's size relative to the star, and the apparent size of the planet changes with its distance from the observer.

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The electrical force at point A will experienced F = 100 N.

According to the Coulomb's law in electrostatics, the Coulomb force acting between two charges is directly proportional to the product of two charges and inversely proportional to the square of distance between them.

Case I :

F = 400 N, d = 30 + 15 = 45 cm

400 ∝ 1/ 15^2

400 ∝ 1/225    ..... (1)

Case II:

Let F be the force, d = 30 cm

F ∝ 1/30^2

F ∝ 1/900     ....(2)

Dividing equation (2) by equations (1), we get

F / 400 = 225 / 900

F = 90000 / 900

F = 100 N

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When a sound gets louder, the following factors change:

a. Intensity

d. Decibel level

f. Amplitude

When a pitch gets higher, the following factors change:

c. Frequency

e. Wavelength

Sound is a type of energy that is transmitted through the vibration of the particles in a medium. When sound is produced, it has characteristics such as frequency, intensity, and amplitude. Changes in these characteristics can result in a different perception of sound by our ears.

When a sound gets louder, the intensity, decibel level, and amplitude of the sound waves increase. Intensity is the amount of energy per unit area that a sound wave carries while the amplitude is the maximum displacement of particles from their equilibrium position. The decibel level also increases with an increase in sound intensity.

When the pitch of a sound gets higher, the frequency of the sound waves increases. Frequency is the number of complete cycles of a wave that occur per second. The wavelength of the sound waves also decreases with an increase in frequency. The speed of sound waves does not change when the pitch of a sound gets higher.

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