25. A circular disk of radius 0.015 m rotates with a constant angular speed of 5.0 rev/s. What is the acceleration of a point on the edge of the disk?
A) 0.31 m/s2
B) 1.6 m/s2
C) 9.9 m/s2
D) 15 m/s2
E) zero m/s2

An electron with a rest mass energy of 0.511 MeV traveling at a speed of 0.5c (where c is the speed of light) has a kinetic energy given by the relativistic kinetic energy formula:

K.E. = (γ - 1)mc^2

where γ (gamma) is the Lorentz factor, m is the mass of the electron, and c is the speed of light.

First, calculate the Lorentz factor using the formula:

γ = 1 / √(1 - v^2/c^2)

For v = 0.5c, γ = 1 / √(1 - (0.5c)^2/c^2) = 1 / √(1 - 0.25) = 1 / √(0.75) ≈ 1.155

Now, calculate the kinetic energy:

K.E. ≈ (1.155 - 1)(0.511 MeV) ≈ 0.155 * 0.511 MeV ≈ 0.079 MeV

Thus, the kinetic energy of the electron traveling at 0.5c is approximately 0.079 MeV.

Learn more about Lorentz factor here:

https://brainly.com/question/24568887

#SPJ11

The kinetic energy of an electron can be calculated using the formula:

KE = (γ - 1) * m0 * c^2

where γ is the Lorentz factor, m0 is the rest mass of the electron, and c is the speed of light.

The Lorentz factor is given by:

γ = 1 / sqrt(1 - v^2/c^2)

where v is the velocity of the electron.

In this case, the rest mass energy of the electron is 0.511 MeV, which is equivalent to 0.511 * 10^6 electron volts (eV).

The speed of the electron is 0.5c, where c is the speed of light.

So, we can first calculate the Lorentz factor:

γ = 1 / sqrt(1 - (0.5c)^2/c^2)

γ = 1 / sqrt(1 - 0.25)

γ = 1.1547

Next, we can calculate the kinetic energy:

KE = (γ - 1) * m0 * c^2

KE = (1.1547 - 1) * 0.511 * 10^6 eV

KE = 0.1547 * 0.511 * 10^6 eV

KE = 78,983.7 eV

Therefore, the kinetic energy of the electron is approximately 78,983.7 electron volts (eV).

To know more about kinetic energy of an electron :

https://brainly.com/question/30544790

#SPJ11

False. Once an object is in motion in the absence of any external forces, it will remain in motion with the same speed and direction. This is known as the law of inertia, one of Newton's laws of motion.

An external force is required only to change the motion of an object. For example, if a ball is rolling on a frictionless surface, it will continue to roll indefinitely in a straight line with a constant speed if there are no other forces acting on it. However, if a force such as friction or gravity acts on the ball, it will change its motion by slowing down or changing its direction. In such cases, an external force is required to maintain the motion of the object in a specific way. Therefore, the statement is false as an object in motion can remain in motion without the application of a force.

Learn more about external forces here:

https://brainly.com/question/16186958

#SPJ11

Dust that is heated to 30 K will emit a blackbody spectrum that peaks at d. 100μm . It is given by Wein's Displacement Law.

According to Wien's Law, which bears the name of German physicist Wilhelm Wien, objects with varying temperatures emit spectra with varied peak wavelengths. Shorter wavelength radiation is emitted by hotter things, giving them their blue appearance. Similar to this, cooler things release longer wavelength light, giving them a reddish appearance. In 1893, Wilhelm Wien developed the Wien's law, also known as the Wien's displacement law, which asserts that different wavelengths of black body radiation have temperature peaks that are inversely proportional to temperatures. Wien's constant is a physical constant that describes the correlation between the black body's thermodynamic temperature and wavelength.

The wavelength at which a blackbody emits the maximum radiation is given by Wien's Displacement law, which is described by

λmax = [tex]\frac{2898}{T}[/tex],

where λmax is the peak wavelength in micrometers, and T is the temperature in kelvins.

For a dust particle heated to 30 K, this would give a peak wavelength at λmax = 2898/30 ≈ 96.6 µm.

So the correct answer is d. 100 µm.

To know more about Blackbody, visit:

https://brainly.com/question/28644935

#SPJ1

Cosmic rays are subatomic particles that travel close to the speed of light.

They are high-energy particles that originate from outside our solar system and even outside our galaxy. Cosmic rays can include protons, electrons, and atomic nuclei. They can also include gamma rays, which are a type of electromagnetic radiation similar to X-rays. These particles are mostly made up of a combination of protons, electrons and other atomic nuclei that have been accelerated to extremely high speeds. They travel through space at near the speed of light, and when they enter the Earth's atmosphere, they interact with the molecules in the air and produce showers of secondary particles. Cosmic rays have been found to come from various sources in nature, including supernovae, pulsars, black holes, active galactic nuclei, and even from mysterious dark matter particles.

Learn more about Cosmic rays Refer: https://brainly.com/question/13960192

#SPJ11

Therefore, the ampacity of four current-carrying No. 8 THHN conductors installed in an ambient temperature of 100 degrees F is approximately 45.5 amps per conductor. The ampacity of four current-carrying No. 8 THHN conductors installed in an ambient temperature of 100 degrees F is determined by referring to the National Electrical Code (NEC) table 310.15(B)(16). For No. 8

THHN conductors, the base ampacity is 50 amps at 30°C (86°F). However, since the ambient temperature is 100°F, we need to apply a temperature correction factor.

For THHN insulation with a 90°C rating, the temperature correction factor at 100°F (38°C) is approximately 0.91. To calculate the adjusted ampacity, multiply the base ampacity by the temperature correction factor:

Adjusted Ampacity = Base Ampacity × Temperature Correction Factor
Adjusted Ampacity = 50 amps × 0.91
Adjusted Ampacity ≈ 45.5 amps

Therefore, the ampacity of four current-carrying No. 8 THHN conductors installed in an ambient temperature of 100 degrees F is approximately 45.5 amps per conductor.

To know more about National Electrical Code click here:

https://brainly.com/question/17215290

#SPJ11

There is a constant, equal electric field throughout. As a result, potential energy is equal.

To determine whether or not EPE is rising, follow this general guideline: A charge's electric potential energy is decreasing if it is travelling in the direction that it would typically go. A charge's electric potential energy increases if it is pushed in the opposite direction from how it would ordinarily travel.

When a charge q is transported from point A to point B, the potential difference between the two places is defined as the change in potential energy of the charge divided by the charge, or V = VB - VA. Voltage, also known as potential difference, is denoted by the letter V.

to know more about potential energy here:

brainly.com/question/24284560

#SPJ1

The most famous prehistoric astronomical observatory is likely Stonehenge in Wiltshire, England. Located in Wiltshire, England, Stonehenge is an iconic prehistoric monument that served as an astronomical observatory, allowing ancient people to track the movements of the sun, moon, and stars.

This ancient site, constructed over 4,000 years ago, features a circle of standing stones that align with astronomical events such as the solstices and equinoxes. Its purpose and exact use as an observatory is still a topic of debate among historians and archaeologists. Scientists can determine whether or whether the cosmos is expanding, contracting, or remaining static by examining extremely far-off objects. Redshift is the term used to describe this idea.

Learn more about movements here:

brainly.com/question/15446389

#SPJ11

In a two-way ANOVA test, the sum of squares for factor B is based on the sum of the squared differences between the mean for each level of factor B and the overall grand mean. This helps to determine the impact of factor B on the dependent variable while accounting for factor A.

This sum of squares is used to calculate the F-statistic, which helps determine if there is a significant difference between the means of the different levels of factor b.

The sum of squares for factor B is calculated as follows:

SSB = Σ [(Yi•. - Y..)² / (a•.)]

where:

Yi•. is the mean of the response variable for level i of factor B

Y.. is the overall mean of the response variable

a is the number of levels of factor A

The sum of squares for factor b is also used to calculate the total sum of squares for the entire model, which includes both factor a and factor b, and the residual sum of squares, which is the sum of the squared differences between the observed data and the predicted values from the model.

Learn more about ANOVA Test here:

https://brainly.com/question/30127764

#SPJ11

Failure to adequately seal well casings is one of the most frequent causes of contamination of wells bored through rock, clay, or hardpan.

Well casings are used to seal off the surrounding soil and rock, protecting wells from contamination. Contaminants can enter into the gaps and cracks.

This is a typical issue in wells that are dug through rock, clay, or hardpan, where the soil is less permeable and less effective in filtering out impurities. It is crucial to properly seal well casings since tainted well water can be dangerous to both humans and animals' health. Well casings can be kept clean and tested regularly to help against contamination.

To know more about Contamination, visit,

https://brainly.com/question/28237583

#SPJ4

The tension is zero when the pendulum is at its highest point (90 degrees with respect to the vertical) and at its lowest point (also 90 degrees with respect to the vertical).

Therefore, the correct answer is: The tension is zero at the angles +90 degrees and -90 degrees.
The tension is never zero.

When a pendulum is swinging, the tension in the string or rod will always be present as it supports the weight of the pendulum bob and provides the centripetal force required for the swinging motion. The tension will be the least when the pendulum is at its lowest point (angle = 0°), but it will never be equal to zero.

To know more about Pendulum click here .

brainly.com/question/14759840

#SPJ11

The  diameter of the U.S. dime when expressed in nanometers is 1.8 x 10^7 nm, which corresponds to option B).

The diameter of an object is the distance across the object passing through its center, measured in units such as millimeters (mm), centimeters (cm), or meters (m). In the case of the U.S. dime, the diameter was changed to approximately 18 mm in 1828.

To convert this diameter to nanometers (nm), we need to use the conversion factor that relates millimeters to nanometers. One millimeter is equal to one million nanometers (1 mm = 1,000,000 nm).

So, to convert 18 mm to nanometers, we can multiply 18 by 1,000,000 as follows:

18 mm * 1,000,000 nm/mm = 18,000,000 nm

Therefore, the diameter of the U.S. dime when expressed in nanometers is 1.8 x 10^7 nm, which corresponds to option B).

Visit to know more about Diameter:-

brainly.com/question/23220731

#SPJ11

The tangential speed of Nairobi, Kenya, near the equator is approximately 465 m/s .

To calculate the tangential speed of Nairobi, Kenya, which is a city near the equator, we will use the following formula:
Tangential speed (v) = 2 × π × radius (r) / time period (T)
Here, the equatorial radius of the Earth (r) is 6,380 km (which we need to convert to meters), and the Earth completes one revolution in 23.93 hours (which we need to convert to seconds).
1. Convert the radius to meters:
r = 6,380 km * 1,000 m/km = 6,380,000 m
2. Convert the time period to seconds:
T = 23.93 hours * 60 min/hour * 60 s/min = 86,078.8 s
3. Calculate the tangential speed:
v = (2 × π × 6,380,000 m) / 86,078.8 s ≈ 465 m/s
So, the tangential speed of Nairobi, Kenya, near the equator is approximately 465 m/s. The correct answer is E) 465 m/s.

learn more about tangential speed Refer: https://brainly.com/question/17689540

#SPJ11

One example of a chemical that is frequently applied just prior to filtration is a coagulant.

Coagulants or flocculants are chemicals that are commonly used in water and wastewater treatment processes to aid in the removal of suspended particles, colloids, and other impurities from water or wastewater. These chemicals are typically added just prior to the filtration step in the treatment process.

Coagulants are substances that cause destabilization and aggregation of suspended particles and colloids in water, leading to the formation of larger particles called flocs. These flocs can be easily removed by sedimentation or filtration. Common coagulants used in water treatment include aluminum sulfate (alum), ferric chloride, and polyaluminum chloride (PAC).

Flocculants, on the other hand, are substances that promote the aggregation of smaller flocs into larger, settleable flocs. They help to speed up the sedimentation process and improve the efficiency of solid-liquid separation. Flocculants are typically used in conjunction with coagulants to enhance the overall performance of the water treatment process.

To know more about filtration ,

https://brainly.com/question/31504556

#SPJ11

A group of stars that form a pattern are called a constellation. This pattern of stars (B) stays together and seems to move as a unit is the correct option, because Asterism is the name for a collection of stars that form a pattern.

It is also known as a constellation, and astronomers use the phrase to describe a region of the sky. An area of the celestial sphere known as a constellation is one in which a collection of discernible stars appears to create a pattern or outline, generally resembling an animal, mythological figure, or inanimate object.

The first constellations probably have their origins in prehistoric times. They were used by people to share tales about their beliefs, encounters, creations, or mythology. Before the current constellations were acknowledged worldwide, various cultures and nations adopted their own constellations, some of which persisted into the first decade of the 20th century. Over time, there have been substantial changes in how constellations are recognised. Many had size or shape changes. Some gained popularity,

Therefore, the correct option is (B).

To know more about constellation

https://brainly.com/question/16724540

#SPJ4

According to the question the new resonant frequency will be larger than it was before.

Frequency is a measure of how often a given event or phenomenon occurs, typically measured as the number of times it occurs in a given period of time. It is usually expressed as the number of occurrences per unit of time, such as per second, minute, day, week, or year. Frequency is an important concept in many areas of physics, mathematics, and engineering.

The resonant frequency of a stretched string is determined by its length and tension. When the distance between the two bridges is increased, the length of the string is increased and the resonant frequency will also increase. Therefore, the new resonant frequency will be larger than it was before.

Therefore, the correct option is C
To learn more about frequency
https://brainly.com/question/254161
#SPJ4

With the prevailing wind is the direction of operation of a sanitary landfill. This is because landfills produce a significant amount of unpleasant odors and gases such as methane.

This create public health concerns and environmental pollution. The direction of operation should be aligned with the prevailing wind direction, so that the wind can carry the odors and gases away from populated areas and sensitive receptors, such as schools and residential areas. . Modern landfills are engineered with several layers of protective liners, such as clay or synthetic materials, to prevent contaminants from leaching into the surrounding soil and groundwater. Landfills also have systems for collecting and treating leachate, which is the liquid that forms as rainwater percolates through the waste. Methane, which is a potent greenhouse gas, is generated as organic matter in the landfill decomposes. Modern landfills are equipped with gas collection systems that capture methane and other gases and use them to generate electricity or heat. This process, called landfill gas-to-energy, helps to reduce greenhouse gas emissions and provides a source of renewable energy.

Learn more about  organic matter here:

https://brainly.com/question/29232090

The statement is referring to the grounding requirements for cases or frames of instrument transformers. The statement is true.

The statement is referring to the grounding requirements for cases or frames of instrument transformers. In general, cases or frames of instrument transformers are required to be grounded to provide a safety path for fault currents and to prevent electrical shock to personnel. However, there are exceptions to this requirement.

According to the National Electrical Code (NEC) 250.172, cases or frames of instrument transformers are not required to be grounded under certain conditions. One of these conditions is when the cases or frames are accessible only to qualified persons. This means that the cases or frames are located in an area that is restricted to authorized personnel who have the knowledge and training necessary to work safely with electrical equipment.

Another condition under which cases or frames of instrument transformers are not required to be grounded is when they are used exclusively to supply current to meters and the primary voltage is not over 150 volts to ground. In this case, the risk of electrical shock is considered low because the voltage is relatively low and the current is limited to the metering circuit.

It is important to note that these exceptions apply only to cases or frames of instrument transformers, and not to other types of electrical equipment. Also, even when cases or frames of instrument transformers are not required to be grounded, it is still a good practice to ground them for added safety.

Visit to know more about Transformer:-

brainly.com/question/29665451

#SPJ11

1V voltage is there across a 100 mH inductor if the current is changing at 10.0 mA/s

The voltage across an inductor is given by the equation V = L(di/dt), where V is the voltage, L is the inductance, and (di/dt) is the rate of change of current with respect to time.

In this case, the inductance is 100 mH (millihenries), and the current is changing at a rate of 10.0 mA/s (milliamperes per second). Converting the inductance to henries (H), we get L = 0.1 H.

Plugging these values into the equation, we get:

V = L(di/dt) = (0.1 H)(0.010 A/s) = 0.001 V = 1 mV

Therefore, the voltage across the inductor is 1 mV or 0.001 V.

learn more about inductor here:

https://brainly.com/question/15893850

#SPJ11

Imagine that you took a road trip. Based on the information in the table, what was the average speed of your car? 195 Time Mile marker 3:00 pm 28 8:00 pm Express your answer to three significant figures and include the appropriate units.

Based on the information in the table, we can calculate the total distance traveled by subtracting the initial mile marker from the final mile marker. 155 32 123 miles We can calculate the total time traveled by subtracting the starting time from the ending time. 8:00 pm 3:00 pm 5 hours to find the average speed, we can divide the total distance traveled by the total time traveled. 123 miles 5 hours 24.6 miles per hour Therefore, the average speed of the car during the road trip was 24.6 miles per hour.

learn more about Based here

https://brainly.com/question/8617708

#SPJ11

The average cross-sectional area of the block is 3.5 cm².

We can start by calculating the volume of the iron block that is submerged in the water. Since the block is 6 cm long and fully submerged, its volume is:

V = A x L

where A is the cross-sectional area of the block and L is its length.

Next, we can use the volume of water displaced by the block to find the volume of the block:

V_block = V_water_displaced

where V_water_displaced is the difference between the final and initial volumes of water in the cylinder:

V_water_displaced = 81 cm³ - 60 cm³

                                = 21 cm³

Therefore, we have:

A x L = 21 cm³

To find the average cross-sectional area of the block, we need to divide both sides of the equation by the length of the block:

A = 21 cm³ / 6 cm

   = 3.5 cm²

Therefore, the average cross-sectional area of the block is 3.5 cm².

Learn more about Cross sectional area at

brainly.com/question/20532494

#SPJ1

The term "RAD" in physics means radiation absorbed dose (option D).

Radiation absorbed dose is one of the two units used to measure the amount of radiation absorbed by an object or person.

RAD reflects the amount of energy that radioactive sources deposit in materials through which they pass.

The radiation-absorbed dose (rad) is the amount of energy (from any type of ionizing radiation) deposited in any medium (e.g., water, tissue, air).

An absorbed dose of 1 rad means that 1 gram of material absorbed 100 ergs of energy (a small but measurable amount) as a result of exposure to radiation.

Learn more about radiation absorbed dose at: https://brainly.com/question/12741652

#SPJ1

True. Frequency scaling refers to increasing the clock speed of a processor to improve its performance.

However, as the frequency increases, the power consumption and heat generated by the processor also increase. This can lead to concerns about power density, which is the amount of power per unit area. To address these concerns, core scaling has become a more popular approach to improving processor performance. This involves adding more processor cores to a chip, rather than simply increasing the frequency of a single core. This allows for better performance while keeping power density under control.

learn more about frequency Refer: https://brainly.com/question/30783512

#SPJ11

The direction of the magnetic field in this region is along the -z-axis (option B).

To determine the direction of the magnetic field when an electron moving along the +x-axis experiences a magnetic deflection in the -y direction, we can use the right-hand rule.

1: Point your thumb in the direction of the electron's motion, which is along the +x-axis.
2: Point your index finger in the direction of the magnetic force experienced by the electron, which is in the -y direction.
3: Your middle finger will point in the direction of the magnetic field.

Following these steps, your middle finger will point along the -z-axis.

You can learn more about the magnetic field at: brainly.com/question/11514007

#SPJ11

HAZWOPER requirements apply to voluntary clean-ups at uncontrolled hazardous waste sites.

Therefore the answer is a. voluntary clean-ups at uncontrolled hazardous waste sites

This is because HAZWOPER (Hazardous Waste Operations and Emergency Response) is a set of regulations established by OSHA (Occupational Safety and Health Administration) to protect workers who are involved in hazardous waste operations and emergency response. These regulations apply to workers who are involved in the cleanup, treatment, storage, and disposal of hazardous waste, as well as those who are involved in emergency response activities.

Voluntary clean-ups at uncontrolled hazardous waste sites fall under the scope of HAZWOPER because they involve the handling of hazardous substances and the potential for exposure to harmful chemicals and materials. The other options, routine sanitary sewer operations, small quantity generators of hazardous waste, and water treatment plant operators, may involve some level of exposure to hazardous substances, but they do not necessarily fall under the scope of HAZWOPER.

To know more on HAZWOPER

https://brainly.com/question/28038347

#SPJ4

According to Table 250.122, for a 600 ampere feeder, a minimum size of 3/0 AWG equipment grounding conductor is required in each of two raceways.
To determine the size of the equipment grounding conductor required in each of the two raceways for a 600-ampere feeder, refer to Table 250.122 in the National Electrical Code (NEC). According to Table 250.122, for a 600-ampere feeder, the required equipment grounding conductor size is 1/0 AWG. Therefore, you would need a 1/0 AWG equipment grounding conductor in each of the two raceways for a 600-ampere feeder.

The National Electrical Code (NEC) is a set of standards for electrical installation and design that is adopted and enforced by state and local governments in the United States. The NEC is published by the National Fire Protection Association (NFPA), and is updated every three years to reflect new technologies, best practices, and safety considerations.

The NEC covers a wide range of topics related to electrical systems, including the installation and use of wiring, grounding and bonding, electrical equipment and appliances, and electrical safety. The code sets forth requirements and guidelines for electrical installations to help ensure that they are safe, reliable, and in compliance with local building codes and regulations.

Visit here to learn more about National Electrical Code brainly.com/question/17215290

#SPJ11

2 TW conductor is installed in a location where the ambient temperature is expected to be 102F and the temperature correction factor for conductor ampacity in this location is 0.82.

The correction factor depends on the type of insulation, the size of the conductor, the number of current-carrying conductors in a raceway or cable, and the type of installation.

The ability of a conductor to carry current decreases, which can result in potential hazards such as overheating and fire. In the case of the 2 TW conductor installed in a location with an ambient temperature of 102°F, the temperature correction factor of 0.82 indicates that the ampacity of the conductor must be reduced by 18%.

This reduction helps ensure that the conductor is not overloaded and can safely carry the required current without exceeding its maximum temperature rating.

Learn more about conductors at

https://brainly.com/question/6531988

#SPJ4

The horizontal we need to use the formula for work done, which is Work = Force x Distance x cos theta in this case, the distance is not given, but we know that the block is moving at a constant speed of 3 meters per second. Distance = Speed x Time. Distance = 3 m/s x 60 s = 180 m

The time given is 1 minute, which is 60 seconds, Distance = 3 m/s x 60 s = 180 m Now we can calculate the work done by the force Of Work = F x Distance x cos theta Since the force is horizontal and the displacement is also horizontal, the angle between them is 0 degrees and cos0 = 1. Work = F x Distance We need to find the value of F. Since the block is moving at a constant speed, the force applied by F must be equal and opposite to the frictional force F = frictional force = 10 N Now we can substitute the values Work = 10 N x 180 m = 1800 J the answer is (E) 1800 J.

learn more about horizontal here.

https://brainly.com/question/30004581

#SPJ11

According to Newton's law of universal gravitation, when the distance between two masses is increased by a factor of 3, the attractive gravitational force between them is decreased by a factor of 9 (3 squared).

This means that the force decreases exponentially as the distance between the masses increases.
According to Newton's law of universal gravitation, when the distance between two masses is increased by a factor of 3, the attractive gravitational force between them is decreased by a factor of 9 (3²).

This is because the gravitational force is inversely proportional to the square of the distance between the masses.

To know more about Newton's Law click here .

brainly.com/question/15280051

#SPJ11

This is due to the fact that when kinetic energy is doubled, the speed of the block increases by the square root of 2, resulting in an increase of 40% in the velocity.

Kinetic energy is the energy of motion. It is the energy that an object has because of its motion. Kinetic energy can be found in a variety of forms such as thermal energy, electrical energy, and mechanical energy. Kinetic energy can be converted into other forms of energy such as potential energy. Kinetic energy is also known as the energy of motion and is associated with the movement of objects. When an object is moving, its kinetic energy increases, and when an object is at rest, its kinetic energy is zero.

Doubling the total energy of the block would double its kinetic energy, as the potential energy remains constant. Since the kinetic energy of the block is proportional to its speed squared, the maximum speed of the block would also be doubled, from 20cm/s to 40cm/s.

To learn more about kinetic energy
https://brainly.com/question/8101588
#SPJ4

Answer:

7m/s

Explanation:

The formula for inelastic collisions is m1*v1 + m2*v2 = (m1+m2)*vf. From this question, we are given m1 = 2500kg, v1 = 14m/s, m2 = 2500 kg, v2 = 0 m/s. Plugging all this into the above equation gets 2500 * 14 = 5000 * vf. Solving that gets vf = 7m/s.

Answer:

v = 7 m/s

Explanation:

Momentum of the first train car before = mass of the first train car x velocity of the first train car

= 2500 kg x 14 m/s

= 35000 kg·m/s

Momentum of the second train car before = mass of the second train car x velocity of the second train car

= 2500 kg x 0 m/s

= 0 kg·m/s

Total momentum before = Momentum of the first train car before + Momentum of the second train car before

= 35000 kg·m/s + 0 kg·m/s

= 35000 kg·m/s

Total mass after = mass of the first train car + mass of the second train car

= 2500 kg + 2500 kg

= 5000 kg

Total momentum before = Total momentum after

35000 kg·m/s = 5000 kg x v

v = 35000 kg·m/s / 5000 kg

v = 7 m/s