Answer:
A physical change involves a change in physical properties. Examples of physical properties include melting, transition to a gas, change of strength, change of durability, changes to crystal form, textural change, shape, size, color, volume and density.
Explanation:
In positron-emission tomography (PET) used in medical research and diagnosis, compounds containing unstable nuclei that emit positrons are introduced into the brain, destined for a site of interest in the brain. When a positron is emitted, it goes only a short distance before coming nearly to rest. It forms a bound state with an electron, called "positronium", which is rather similar to a hydrogen atom. The binding energy of positronium is very small compared to the rest energy of an electron. After a short time the positron and electron annihilate. In the annihilation, the positron and the electron disappear, and all of their rest energy goes into two photons (particles of light) which have zero mass; all their energy is kinetic energy. These high energy photons, called "gamma rays", are emitted at nearly 180° to each other. What energy of gamma ray (in MeV, million electron volts) should each of the detectors be made sensitive to? (The mass of an electron or positron is 9 × 10-31 kg. 1 eV = 1.6 × 10-19 joules.
Answer:
Energy of gamma ray = 506250 eV
Explanation:
We are told that the mass of an electron or positron is 9 × 10-31 kg.
This means that their energies will be the same.
Thus; E_e = E_p
Now, since electron and positron annihilate to form gamma(γ) particle, then using work energy principle, we have;
E_γ + E_γ = E_e + E_p
Thus;
2E_γ = E_e + E_p
Since E_e = E_p, we now have;
2E_γ = 2E_e
Thus;
E_γ = E_e
Since all the energy of the electron is converted, then from Einstein's relativity theory, this implies that;
E_e = mc²
c is speed of light = 3 × 10^(8) m/s
And m is given as 9 × 10^(-31) kg
Thus;
E_e = 9 × 10^(-31) × (3 × 10^(8))^(2)
E_e = 810 × 10^(-16) J
Since E_γ = E_e
Thus;
E_γ = 810 × 10^(-16) J
We are given that; 1.6 × 10^(-19) J = 1eV
Thus; 810 × 10^(-16) J gives;
(810 × 10^(-16) × 1)/(1.6 × 10^(-19)) = 506250 eV
HELPP PLEASEEE Which issue is not a challenge an organism encounters?
A getting energy
B reproducing
C maintaining structure
D regenerating arms
Answer:
regenerating arms....
A freight train consists of two 8.00 \times 10^5~\text{kg}8.00×10 5 kg engines and 45 cars with average masses of 5.50 \times 10^5~\text{kg}5.50×10 5 kg. What force must each engine exert backward on the track to accelerate the train at a rate of 5.00 \times 10^{-2}~\text{m/s}^25.00×10 −2 m/s 2 if the force of friction is 7.50 \times 10^5 ~\text{N}7.50×10 5 N, assuming the engines exert identical forces? This is not a large frictional force for such a massive system. Rolling friction for trains is small, and consequently trains are very energy-efficient transportation systems.
Answer:
F₁ = 4.29 x 10⁵ N
Explanation:
The total force required to move the freight train with the given acceleration is given by the following formula:
F = ma + f
where,
F = Total Force Required from both engines = ?
m = equivalent mass of system = 2(8 x 10⁵ kg) + 5.5 x 10⁵ kg = 21.5 x 10⁵ kg
a = required acceleration = 5 x 10⁻² m/s²
f = force of friction = 7.5 x 10⁵ N
Therefore,
F = (21.5 x 10⁵ kg)(0.05 m/s²) + 7.5 x 10⁵ N
F = 8.575 x 10⁵ N
Now, for identical forces in each engine can be given as:
Force exerted by each engine = F₁ = F/2
F₁ = 8.575 x 10⁵ N/2
F₁ = 4.29 x 10⁵ N
What causes different colors to appear in the sky.
Answer:
The colors of the sunset result from a phenomenon called scattering. Molecules and small particles in the atmosphere change the direction of light rays, causing them to scatter. ... The short-wavelength blue and violet are scattered by molecules in the air much more than other colors of the spectrum.
Explanation:
Answer:
The scattering and reflection of light by dust particles.
if you double the period of a pendulum. what happens to its length?
The only way you COULD double the period would be to make the string 4 times as long as it is now.
The achievement of lifting a rocket off the ground and into space can be explained by
Answer:
The achievement of lifting a rocket off the ground and into space can be explained by Newton's third law of motion. What is required for a rocket to lift off into space? Thrust is required for a rocket to lift off into space, ... An object that travels around another object in space is called a satellite.
Explanation:
1. Why is it important to use units in any graph?
2. Why does any graph need a title on it?
Answer:
so its easier to understand for the reader
Explanation:
2) Labelling. Graphs are used to present data. They must be clearly labelled if the reader is to understand them. By labelling we are referring to the text inside the graph itself, and not the title.
For which scientific method do you use experimental and control groups?
A. Forming a hypothesis
B. Analyzing data
C. Drawing conclusions
D. Conducting an experiment
Answer:
Analyzing data B.
Explanation:
Answer:
D
Explanation:
Oil is a powerful source of energy used for cars, machines, and many other purposes. While studying sources of energy that could replace the use of oil, a student thinks about solar power, wind power, nuclear power, and electric batteries. The students asks, "Which type of source will waste the least energy and provide the most energy in all situations?" Which best describes why a scientist would ask a different question than this one? The question asks about subjective personal preferences regarding energy. The question focuses on the objective measurements of amounts of energy. The question has too wide of a focus, as though all situations can be studied at once. The question is focused on the future and finding new answers about changing needs.
Answer:
The question has too wide of a focus, as though all situations can be studied at once.
Explanation:
Blowing into a flute can produce a sound because
A. light energy is transformed into sound energy
B. the flute warms the air
C. air expands in the flute
D. air in the flute vibrates
Answer:
Choice D
Explanation:
air in the flute causes vibrations which makes sound.
In order for clouds to form, what must happen first?
Answer:
Step 1: Change Water Vapor into Liquid Water
But in order to grow a cloud, we need to get the water vapor from a gas to its liquid form. Clouds begin to form when a parcel of air rises from the surface up into the atmosphere
Explanation:
Which action could a student take to show a transverse wave
A:blow up a balloon
B:shake a rope from side to side
C:shout across a soccer field
D:Knock on a door
Answer:
B is the correct answer
Explanation:
I just did this question
Convert 0.0000505 nanometers into scientific notation
A .25 kilogram baseball is thrown upwards with a speed of 30 meters per second. Neglecting friction the maximum height reached by the baseball is approximately
Answer: 46 meters
Explanation:
The maximum height reached by the base ball is 45.9 meters.
To find the maximum height the given values are,
Mass = 25 Kg
speed v = 30 meters per second.
What is the height of baseball reached?As the ball goes up, it acts due to the gravity.
The gravity slows an upward-moving object,
Acceleration due to gravity = 9.8 m/s every second,
the baseball reaches its greatest height in (30/9.8) = 3.06 seconds.
At that instant, its speed is zero.
The baseball's average speed from toss to peak is
(1/2) (30 + 0) = 15 m/s .
The baseball average speed = 15 m/s
And the time for greatest height = 3.06 seconds.
Substituting the given values,
The ball rises can be calculated as
(15 x 3.06) = 45.9 meters.
Thus, the baseball reached the maximum height approximately is 45.9 meters.
Learn more about the height due to gravity,
https://brainly.com/question/1977173
#SPJ6
7. Which of the following statements concerning a short in a series circuit is true?
O A. A short causes the circuit voltage to increase.
B. A short circuit will draw less current than a properly functioning one.
C. A short circuit is similar to adding another resistor to the circuit.
D. Little or no current will flow through the circuit beyond the point of the short.
Answer:
A circuit that has little or no resistance
Explanation:
Apex
Little or no current will flow through the circuit beyond the point of the short a short in a series circuit .
What is a short in a series circuit?Simply said, a short circuit is a connection with low resistance between the two conductors delivering electricity to any circuit. This leads to an excessive current flow via the "short" in the power source and may potentially result in the power source being destroyed.
When there is a short in a series circuit, the current rises over its typical level. When a component is shorted, the voltage drop across it drops to 0V, while the voltage drop across the intact component rises.
In a series circuit, if there was a short circuit, one of the components would blow up and the circuit, or all the components, would cease to function. All of the lights would consequently go off. That would account for a blackout even if one component had a short circuit.
To learn more about circuit, refer the link:
https://brainly.com/question/29032441
#SPJ6
What is the displacement of the cross-country team if they begin at the school, run 16 kilometers and finish back at the school? Calculate the average speed and average velocity if they finish in 1 hour and 15 minutes?
Which statement is supported by Kepler's laws?
O The closer a planet is to the Sun, the faster it moves.
O The farther a planet is from the Sun, the faster it moves.
O As a planet moves away from the Sun, its gravitational force increases.
O As a planet moves away from the Sun, its gravitational force remains the same.
Answer:
A. The closer a planet is to the Sun, the faster it moves.
Explanation:
According to this law, planets move around the sun in elliptical orbits. An imaginary lines drawn from the center of Sun to center of planets will sweep equal area in equal time interval.
Answer option B,C&D is incorrect because planets that are far away from the Sun take more time to move all around the Sun and experience less gravitational force and move slower than those near the Sun.
Answer:
a
i am never wrong
Please help I don’t know how to do this
Answer:
2.2 m/sExplanation:
formula to be used is: a = ∆v/∆t
where:
a = 0.09 m/s²
∆t = 10 s
∆v = a*∆t
= (0.09 m/s²)(10 s)
= 0.9 m/s
Vivian's final speed:
= initial speed + change in speed
= 1.3 m/s + 0.9 m/s
= 2.2 m/s
A coil is wrapped with 206 turns of wire on the perimeter of a circular frame (of radius 31 cm). Each turn has the same area, equal to that of the frame. A uniform magnetic field is directed perpendicular to the plane of the coil. This field changes at a constant rate from 23 mT to 54 mT in 24 ms. What is the magnitude of the induced average E in the coil, over the time interval 24 ms during which the field changes? Answer in units of V.
Answer:
E = -80.33 V
Explanation:
For this exercise we use Faraday's law of induction
E = - N d[tex]\phi _{B}[/tex] / dt
where the magnetic flux is
\phi _{B} = B A cos θ
In the exercise they indicate that the magnetic field is perpendicular to the coil, therefore the normal of the coil area and the field has the same direction, consequently the angle is zero. Since the area is constant
E = - N A dB / dt
let's look for each term
a =π r²
they tell us that the variation in the field is linear
dB / dT = (B_f-B₀) / t
we substitute
E = - N (π r²) (B_f -B₀) / t
let's calculate
E = - 206 π 0.31² (54 - 23) 10⁻³ / 24 10⁻³
E = -80.33 V
Why can concave mirror is used in cosmetic mirror
In a totally inelastic collision between two equal masses, with one initially at rest, what fraction of the initial kinetic energy is lost
Answer:
50%
Explanation:
Assuming no external forces acting during the collision, total momentum must be conserved.As one of the mass was initially at rest, the initial momentum can be written as follows:[tex]p_{o} = m* v_{1o} (1)[/tex]
If the collision is totally inelastic, both masses must move as one after the collision, so we can write the following equation:[tex]p_{f} = (m+m)* v_{f} = 2*m*v_{f}[/tex] (2)As po = pf, we can solve for vf in terms of v1o, as follows:[tex]v_{f} =\frac{v_{1o}}{2}[/tex]
The initial kinetic energy will be:[tex]K_{1o} =\frac{1}{2} * m *v_{1o}^{2} (1)[/tex]
The final kinetic energy of both masses will be as follows:[tex]K_{f} =\frac{1}{2} * 2*m *(\frac{v_{1o}}{2}) ^{2} (2)[/tex]
Rearranging in (2) we get:[tex]K_{f} =\frac{1}{2} *m *v_{1o} ^{2} *\frac{1}{2} = \frac{K_{1o} }{2}[/tex]
So, the fraction of the initial kinetic energy lost is just the half of the initial value.A roller coaster at the Six Flags Great America amusement park in Gurnee, Illinois, incorporates some clever design technology and some basic physics. Each vertical loop, instead of being circular, is shaped like a teardrop. The cars ride on the inside of the loop at the top, and the speeds are fast enough to ensure that the cars remain on the track. The biggest loop is 40.0 m high. Suppose the speed at the top is 10.8 m/s and the corresponding centripetal acceleration is 2g. (a) What is the radius of the arc of the teardrop at the top
Answer:
5.95 m
Explanation:
Given that the biggest loop is 40.0 m high. Suppose the speed at the top is 10.8 m/s and the corresponding centripetal acceleration is 2g
For the car to stick to the loop without falling down, at the top of the ride, the centripetal force must be equal to the weight of the car. That is,
(MV^2) / r = mg
V^2/ r = centripetal acceleration which is equal to 2g
2 × 9.8 = 10.8^2 / r
r = 116.64 /19.6
r = 5.95 m
A block of wood mass 0.60kg is balanced on top of a vertical port 2.0m high. A 10gm bullet is fired horizontally into the block and the embedded bullet land at a 4.0m from the base of the port. Find the initial velocity of the bullet.
Answer:
Mass of bullet is m=0.01kg
Mass of the block is M=4kg
Coefficient=0.25,distance=20m
So, let the speed of the block just after the bullet embedded in it be V and v be the speed of bullet before striking the block,
By applying conservation of momentum,
mv=(m+M)V
V=
M+m
mv
Explanation:
please mark me as the brainliest answer and please follow me for more answers to your questions..
The initial velocity of the bullet is 382 m/s
The given parameters;
mass of the wood, m₁ = 0.6 kgheight of the port, h = 2mass of the bullet, m₂ = 10 g = 0.01 kghorizontal distance traveled by the bullet, x = 4 mApply the principle of conservation of mechanical energy;
The maximum potential energy of the bullet-wood system at the top of the port = maximum kinetic energy of the system at the base of the port.
[tex]K.E_{max} = P.E_{max}\\\\\frac{1}{2} mv_{max}^2 = mgh_{max}\\\\v^2_{max} = 2gh_{max}\\\\v_{max} = \sqrt{2gh_{max}} \\\\v_{max} = \sqrt{2\times 9.8\times 2} \\\\v_{max} = 6.26 \ m/s[/tex]
Apply the principle of conservation of linear momentum to determine the initial velocity of the bullet;
let the initial velocity of the bullet = u₂[tex]m_1u_1 + m_2u_2 = v(m_1 + m_2)\\\\0.6(0) + 0.01(u_2) = 6.26((0.6 + 0.01)\\\\0.01u_2 = 3.819\\\\u_2 = \frac{3.819}{0.01} \\\\u_2 = 381.9 \ \approx 382 \ m/s[/tex]
Thus, the initial velocity of the bullet is 382 m/s
Learn more here:https://brainly.com/question/24424291
What volume is represented by each small tick mark ? Help !!!
Answer:
In the taller, skinnier cylinder, each tick mark represents 2, while in the larger one, each tick mark represents 50.
Explanation:
If you count the tick marks between each big number, then you can divide, and figure out what amount each tick mark represents.
3. Pencils should not be used inside the computer to change the setting of switches or to
and
pry off jumpers because the tip contains lead which can act as a
may damage the computer Components.
Answer: True
Explanation:
Pencils indeed should not be used as tools when working inside a computer because it is made of Lead.
Lead is a conductor of electricity and as such if it is left inside the computer at even miniscule quantities, it can redirect electricity and damage components in the process.
If one wants to work inside a computer, it is best to use tools like tweezers and needle-nose pliers.
Due to the presence of graphite(A good conductor of electricity), Pencils should not be used inside the computer to change the setting of switches.
What is the meaning of conductors?The conductors are the materials that can allow electricity and heat to pass through them.
Since the pencils are made up of graphite which is a good conductor of electricity. When we use pencils to do something inside the computer circuits and if some portion of the graphite remains on the circuit board.
Now due to the good conducting property of the graphite, it will allow the current to flow and the short circuit of the circuit board can take place which will damage the computer.
Thus due to the presence of graphite(A good conductor of electricity). Pencils should not be used inside the computer to change the setting of switches.
To know more about Conducting materials follow.
https://brainly.com/question/771692
3 general relevant psychology related problems at present
Answer:
Explanation:
Scientific research conducted by psychologists, organized by topics here, can inform and guide those seeking help with issues that affect their professional lives, family relationships and emotional wellness.Tips for choosing a psychotherapist and answers to financial questions related to therapy.
When faced with important events (stressors) which are threatening or very hard to, psychological symptoms of stress include anxiety and tension, uncontrollable. In general, this refers to high levels of suspicion and mistrust, usually seen in this psychological condition is associated with acute physical sickness
plz mark as brainliest
Megan is eating a Snickers and decides not to finish the last it of it. She drops the snickers into a trashcan below. What happens to the speed of the piece of Snickers as it falls towards the trashcan?
Answer:
i like trains 45654
Explanation:
Which is formed by positive ions from a base and negative ions from an acid?
salt
vinegar
soap
carbonate
Answer:a
Explanation:
The formation of salt takes place by the sharing of positive ions from a base and negative ions from an acid. Hence, option (a) is correct.
The given problem is based on the concept and fundamentals of Neutralization. The process of neutralization is the name given to the chemical reaction between that takes place between the acid and base.
An acid is the chemical species having the negative ion, hence also known as anions.And the bases are the chemical species having the positive ions, hence they are also known as cationic species. During the chemical reaction between the acid and base, the positive ions from the base and negative ions from the an acid forms a neutral compound, known as Salt. Therefore, this reaction is also known as neutralization reaction.Thus, we can conclude that the formation of salt takes place by the sharing of positive ions from a base and negative ions from an acid. Hence, option (a) is correct.
Learn more about the Neutralization reaction here:
https://brainly.com/question/16188332
An Object is thrown straight up into the air with an initial velocity of 15m/s. What is its velocity at the peak of its flight?
Answer:
0
Explanation:
The initial velocity of an object is 15 m/s when it was thrown straight up into the air.
At maximum height, the velocity of the object is equal to 0. It starts coming downward after that and falls ground. Height attained by the object is given by :
[tex]h=\dfrac{v^2}{2g}[/tex]
Hence, its velocity at the peak of its flight is equal to 0.
A particular car can go from rest to 90 km/h in 10 s. What is its acceleration? (Report your answer in km/h*s)
Answer: 9 km/h
Explanation:i’m pretty sure
Answer:
Well, it depends on the type of car but a regular car like a toyota 4x4 only goes at 5k/h if the car starts when complete rest