Leap years _____.happen because the Earth revolves around the sun in less than 365 days
make up for the extra one-fourth day the Earth needs to orbit the sun
add an extra day to the end of December, making the month 32 days long
subtract a day from February, making the month only 27 days long

Answer:

2.5 kg

Explanation:

We can solve the problem by using Newton's second law:

[tex]F=ma[/tex]

where

F is the net force acting on the train

m is the mass of the train

a is the acceleration

For the toy train in the problem,

F = 3.0 N

a = 1.2 m/s^2

So we can solve the formula for m, to find the mass of the train:

[tex]m=\frac{F}{a}=\frac{3.0 N}{1.2 m/s^2}=2.5 kg[/tex]

Answer:

2.5

Explanation:

Answer:

Resistance increases with length because the electrons have further to go, so suffer greater collisions with atoms in the material. Look at these wires: Electrons moving through the short wire only feel resistance for a short time compared to the longer one. This means its resistance is less.

Explanation:

Answer:

A longer length leads to a higher resistance

Explanation:

Answer:

The frequency, f, is 250 Hz. Hz is cycles per second. Hence a number divided by seconds.  

The wavelength, λ, is 1.5 m.  

The speed is v. Which is frequency times wavelength.  

v = f xλ  

Hence 250Hz*1.5m= 375 meters per second or 375 m/s

Explanation:

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Explanation:

The expression for the speed of the sound in terms of frequency and the wavelength is as follows;

[tex]v=\nu \lambda[/tex]

Here, v is the speed, [tex]\nu[/tex]  is the frequency of the wave and [tex]\lambda[/tex]  is the wavelength of the wave.

It is given in the problem that a sound wave has a frequency of 250 Hz and a wavelength of 0.35 m.

Calculate the speed of the sound wave.

[tex]v=\nu \lambda[/tex]

Put [tex]\nu= 250 Hz[/tex]  and [tex]\lambda= 0.35 m[/tex].

[tex]v=(250)(0.35)[/tex]

v= 87.5 m/s

Therefore, the speed of the sound wave is 87.5 m/s.

Answer:

CaCo3 contains carbon, oxygen and calcium.

Explanation:

Calcium carbonate (CaCO3) is a compound made up of calcium, carbon, and oxygen in a 1:1:3 ratio. It consists of a metal (calcium) and nonmetals (carbon and oxygen), and is an example of an inorganic compound commonly found in materials like cement.

The compound calcium carbonate is represented by the formula CaCO3. It is a compound, not an element, because it is made up of more than one type of atom chemically bonded together. The elements found in this compound are calcium, carbon, and oxygen.

In the chemical formula of calcium carbonate, the ratio of calcium (Ca) to carbon (C) to oxygen (O) atoms is 1:1:3, indicating that there is one calcium atom, one carbon atom, and three oxygen atoms.

The names of these substances are as follows:

The names of the compounds listed are:

Inorganic compounds often consist of a metal and nonmetals. For instance, calcium carbonate involves the metal calcium and the nonmetals carbon and oxygen.

The compound names for the given chemical formulas are:

Answer:

15

Explanation:

Answer:

The speed of the light ray is halved

Explanation:

The index of refraction of a medium is the ratio between the speed of light in a vacuum (c) and the speed of light in the medium (v):

[tex]n=\frac{c}{v}[/tex]

For medium X, we have

[tex]n_x=\frac{c}{v_x}[/tex] (1)

For medium Y, we have

[tex]n_y=\frac{c}{v_y}[/tex] (2)

Dividing (1) by (2), we find

[tex]\frac{n_x}{n_y}=\frac{v_y}{v_x}[/tex] (3)

In this problem, the index of refraction of medium Y is twice as great as the index of refraction of medium X:

[tex]n_y = 2 n_x[/tex]

Substituting this into eq.(3), we get

[tex]\frac{n_x}{2n_x}=\frac{v_y}{v_x}\\v_y = \frac{v_x}{2}[/tex]

So, as a light ray travels from medium X into medium Y, the speed of the light ray is halved.

From the calculation, the speed of the light ray is halved.

The term refractive index refers to the ratio of the speed of light in one medium to the speed of light in another medium. We are told that the speed of light in medium Y is twice as great as the absolute index of refraction of medium X.

Let;

refractive index of X be nx

refractive index of y be ny

speed of light in x by vx

speed of light in y be vy

nx/ny = vx/vy

But ny = 2nx

nx/2nx =  vx/vy

1/2 =  vx/vy

vy = vx/2

Hence, we can see that the speed of the light ray is halved.

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I think the answer should be the last one. Magnets attract magnets with unlike poles and repel magnets with like poles

Answer:

480 mL

Explanation:

Ideal gas law states:

PV = nRT

At constant pressure, nR/P is constant.  Therefore:

V / T = V / T

420 mL / 220 K = V / 250 K

V ≈ 480 mL

Answer:

Angle of incidence

Explanation:

The diagram shows the reflection of a light ray.

When a light ray undergoes reflection:

- The incident ray, the reflected ray and the normal to the surface all lie in the same plane

- The angle of reflection is equal to the angle of incidence

The two angles are defined as follows:

- The angle of incidence is the angle between the incident ray and the normal to the surface (1)

- The angle of reflection is the angle between the reflected ray and the normal to the surface

In the picture, we see that the angle marked with X corresponds to the angle defined in (1), so it is the angle of incidence.

Answer:

The magnitude of the electric field is 800 N/C and the direction is positive and points to the right.

Explanation:

Ok, here is the explanation:

The magnitude of the electric field is simply defined as the force per charge on the test charge:

[tex]electric field strength=\frac{force}{charge}[/tex]

If the electric field strength is denoted by the symbol E, then the equation can be rewritten in symbolic form as:

[tex]E=\frac{F}{q}[/tex]

and this is the equation we are going to use to solve the problem

We have: E=?, q=+50μC and F=0.040N

We know that 1C=1x10-6 μC so 50μC is equal to 5x10-5 C or 0.00005 C

Then we use the equation as follows:

[tex]E=\frac{0.040}{+0.00005} =800 \frac{N}{C}[/tex]

Because the charge is positive and also the force applied, so will the electric field. And since the force points to the right, the electric field as a vector points to the right.

Answer:

EFFECTS: ( doughts)

EFFECTS:( FLOODS)

How to prevent from flooding is :

How to prevent from droughts :

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There are two conditions necessary for total internal reflection, which is when light hits the boundary between two mediums and reflects back into its original medium:

Light is about to pass from a more optically dense medium (slower) to a less optically dense medium (faster).

The angle of incidence is greater than the defined critical angle for the two mediums, which is given by:

θ = sin⁻¹([tex]n_{fast}[/tex]/[tex]n_{slow}[/tex])

Where θ = critical angle, [tex]n_{fast}[/tex] = refractive index of faster medium, [tex]n_{slow}[/tex] = refractive index of slower medium.

Choice C gives one of the above necessary conditions.

Answer:

C. Light in a medium is incident on a boundary with a faster medium.

Explanation:

Answer:

a.

Explanation:

Alkali metals, including elements like sodium and potassium, are extremely reactive due to each having a single valence electron in their outermost shells. This electron is easily removed to form a relatively stable, singularly positive ion, thus making them highly reactive.

Alkali metals, being part of Group 1 of the periodic table, are known for their high reactivity due to their atomic structure. This family includes elements like sodium and potassium. They all share an atomic feature which is having a single valence electron in the outermost shell (s electron in ans configuration). This specific feature is what makes alkali metals highly reactive.

The single valence electron is loosely held by the atom and can be easily removed. When this happens, the alkali metal atom forms a relative stable and singularly positive ion (cation). The ease of losing this valence electron, paired with the large atomic radii and the lowest first ionization energy in their periods, gives alkali metals their characteristic high reactivity.

A common trait within the group is that the reactivity increases with higher atomic numbers due to the decreasing ionization energy. In contrast to alkali metals, alkaline earth metals of Group 2 have a completed s subshell in outermost shell, making them less reactive, but still amongst the most reactive elements.

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Answer:

1. Electric current

2. In fact it is electrons that flow through a metallic conductor, and they flow from the negative terminal to the positive terminal

3. Series and parallel

4. Series

5. Parallel

6.

7.

8.A fuse is a small, thin conductor designed to melt and separate into two pieces for the purpose of breaking a circuit in the event of excessive current. A circuit breaker is a specially designed switch that automatically opens to interrupt circuit current in the event of an overcurrent condition.

9.

10. The power of batteries in a circuit. The key functions of a battery and bulb in a circuit are explained. A battery is a source of energy which provides a push - a voltage - of energy to get the current flowing in a circuit. A bulb uses the electrical energy provided by the battery, but does not use current.

The flow of electrons through wires and components is known as electric current.

Electricity is defined as a form of energy occurring naturally due to motion and interactions of electrons.

Here,

1. The flow of electrons through wires and components is known as electric current. Or simply, electric current is the rate of flow of charge.

2. Since, the electrons are attracted to the positive terminal of the battery, they move from the negative to the positive terminal of the battery.

The direction of conventional flow of current is taken opposite to the flow of electrons. Thus electric current flows from positive terminal to the negative terminal of the battery. So, it is true.

3. The two main types of circuits are series and parallel.

4. The  type of circuit in which there is only one path for an electric current to flow is known as a series circuit.

5. The type of circuit would allow an electric current to continue to flow even if a single path is broken is a parallel circuit.

6. The diagram of a series circuit is attached.

7.  R' = 3 Ω  

 The equivalent resistance of the 4 resistors,

   R(eff) = 4R' = 4 x 3

   R(eff) = 12 Ω  

8. The purpose of fuses and circuit breakers is to protect equipment by stopping the flow of electric current.

9. The symbol represents the cell in a circuit diagram.

10. The purpose of a cell (battery) is to store chemical energy and transfer it to electrical energy when a circuit is connected.

Hence,

The flow of electrons through wires and components is known as electric current.

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Your question was incomplete. Attaching the image here.

They tend to be lustrous, ductile, malleable, and good conductors of electricity, while nonmetals are generally brittle (for solid nonmetals), lack lustre, and are insulators.

You just said "constant speed", and "straight line" which means constant direction.

"Acceleration" means any change of speed or direction of motion.  Since neither of those is changing, no acceleration is happening.

Acceleration is the rate of change of velocity. Constant velocity, means there is no change in velocity and hence the plane is not accelerating.

Velocity is a physical quantity used to measure the distance traveled per unit time. Thus, velocity is the ratio of distance to the time of travel. Velocity is a vector quantity and it is expressed in the units m/s, km/h, miles/hr, ft./s etc.

The rate of change of velocity is called acceleration. Acceleration is also a vector quantity thus having both magnitude and direction. As change in velocity per time difference is the acceleration and it is expressed in the unit m/s².

Here, the plane is moving through  a straight line at a constant speed of 500 mph. Thus no change in velocity indicates the plane is not accelerating in any direction.

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Answer:

The technique in which people use machines to learn how to control their bodies is known as D, Biofeedback.

Explanation:

Biofeedback is a variety of different machines that help people learn how to control their bodies depending on their specific needs, varying from things like scalp sensors, electrocardiographs, electromyographs and more.

Answer:

biofeedback

Explanation:

Answer:

B. Wave B has greater intensity and transfer more energy.

Explanation:

Amplitude of wave B is more and it seems to be compact in less period of time as compared to Wave A.

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Answer:

medium. A medium is the intervening substance through which impressions are conveyed to the senses or a force acts on objects at a distance.

1) Impulse: -32,000 kg m/s

The impulse acting on the car is equal to the change in momentum of the car:

[tex]I= \Delta p = m (v-u)[/tex]

where in this problem we have

m = 1000 kg is the mass of the car

v = 0 m/s is the final velocity of the car

u = 32 m/s is the initial velocity of the car

Substituting values into the equation, we find

[tex]I=(1000 kg)(0-32 m/s)=-32,000 kg m/s[/tex]

2) -4751 N

The impulse exerted on the car is also equal to the product between the average force, F, and the duration of the collision, t:

[tex]I=Ft[/tex]

where in this situation we know

[tex]I=-32,000 kg m/s[/tex] is the impulse

t = 7 s is the duration of the collision

Solving the formula for F, we find the average force:

[tex]F=\frac{I}{t}=\frac{-32,000 kg m/s}{7 s}=-4,571 N[/tex]

and the negative sign means that the force is in the opposite direction to the motion of the car.

Answer:

43.4 s

Explanation:

First of all, we can find the acceleration of the train by using the equation:

[tex]v^2 -u^2 = 2ad[/tex]

where

v = 39.9 m/s is the final speed

u = 18.2 m/s is the initial speed

a is the acceleration

d = 1250 m is the distance covered

Solving for a,

[tex]a=\frac{v^2-u^2}{2d}=\frac{(39.9 m/s)^2-(18.2 m/s)^2}{2(1250 m)}=0.50 m/s^2[/tex]

And now we can fidn the time taken, by using the formula:

[tex]a=\frac{v-u}{t}\\t=\frac{v-u}{a}=\frac{39.9 m/s-18.2 m/s}{0.50 m/s^2}=43.4 s[/tex]

Answer:

Period of the wave: [tex]T = 0.4 \text{ seconds}[/tex]

Frequency of the wave: [tex]f = 2.5 \text{ Hz}[/tex]

Explanation:

Period of the wave:To calculate the period of a wave from a displacement vs time graph we identify the amount of time it takes for one cycle to be completed. According to the graph, 1 cycle is completed in 0.4 seconds, so:

[tex]T = 0.4 \text{ seconds}[/tex]

Frequency of the wave: To find frequency we simply calculate the inverse of the period because we know the relationship [tex]T= \frac{1}{f}[/tex] or [tex]f = \frac{1}{T}[/tex]

[tex]f= \frac{1}{T}= \frac{1}{0.4 s}= 2.5 \text{ Hz}[/tex]

The answer is 12 ....

1. A. The relative motion between Earth and the Sun

The Earth is constantly moving, be it around its own axis, or around the Sun. As it moves around the Sun over the course of one year, the Earth changes its relative position toward the constellations. This results in different positions of the constellations in different periods of the year, when it comes to viewing them from the Earth of course. It looks for the ordinary observer that the constellations are making lot of movement throughout the year and change their positions, and they do move, just not in that manner, but in fact it is the relative motion between the Earth and the Sun that gives that effect on the night sky.

2. A. Interstellar medium

The galaxies are composed of multiple basic things, with the stars and the interstellar medium being the dominant ones. Apart from these two there are also gases and dust. The galaxies are massive, and even the smallest of them are so big that we can not even imagine in our minds as we don't have a scale in our minds for something so large. They have trillions of stars in them, and the majority of the space between the stars is filled with interstellar medium.

3. B. Expand

The Big Bang theory is the most widely accepted theory about the formation of the universe, even though it doesn't really has proper explanations for certain things. This theory suggests that everything managed to get dragged into a single miniature spot and once the gravity became way to big, an explosion occurred. This explosion was so big, and everything moved so quickly, that in literary thousands of parts of a second millions of light years of space were filled in. Everything was practically expanding from the spot of explosion, expanding outwards, giving the basis for the formation of everything we see in the universe. The process of expanding is still continuing, as we can see with the quasars, and it is expected to do so in the future.

4. C. Low-mass main sequence

From what has been observed from the space until now, it seems that the low-mass main sequence stars are the once that dominate the universe by far, at least in numbers. These stars are also called red dwarfs. They are small stars, having reddish color, and their mass is also relatively low compared to the bigger stars. It is estimated that around three quarters of the stars are actually of this type. Unfortunately, because they are small and their low luminosity, individual stars of this type can not be seen from the Earth with naked eye.

5. A. Rocky

The terrestrial planets are planets that are small in size. They are closer to the Sun, thus they are warmer because of it. Unlike their Jovian counterparts, the terrestrial planets tend to be denser, but also what is a striking distinction is that they are rocky. These planets have rocky surfaces, thus their surfaces are solid, covered with numerous types of geologic features, while the Jovian do not have rocky surface, but instead it is gaseous or icy. The fact that these planets are rocky, also gave big advantage to them when it came to providing conditions for life, and the Earth was the lucky one that had all other things in place and boomed with life.

6. B. The Moon's gravity pulls on Earth's oceans, causing tides

The Moon is very close to the Earth, and it is actually a very large moon for the size of the Earth. It has its own gravity of course, and the sheer proximity means that it will influence on something. Since the gravitational pull of the Earth is stronger, the gravitational pull of the Moon can not do something spectacular, but at least it manages to pull the ocean waters. As it pulls the ocean waters, the Moon's gravity actually cause the high tides and low tides.

Final answer:

The different constellations visible during the year result from Earth's motion around the sun. Galaxies contain interstellar medium alongside stars. After the Big Bang, the universe began expanding. Low-mass main sequence stars are the most common. Terrestrial planets are rocky and affected by the moon's gravitational pull, which causes tides.

Explanation:

Different constellations are visible at different times of year because of A. The relative motion between Earth and the sun.

A galaxy is composed of stars and A. Interstellar medium.

Once the Big Bang occurred, everything in the universe started to B. Expand.

The most common stars are C. Low-mass main sequence stars.

Unlike Jovian planets, the terrestrial planets are small, dense, and A. Rocky.

The gravitational force of the moon affects Earth as B. The moon's gravity pulls on Earth's oceans, causing tides.

Answer:

A) 4.29%

Percentage error is 4.29%

Explanation:

From the experiment results;

The mass of water = 15.32 g - 14.65 g

                               = 0.67 g

Therefore;

The percentage error in the experiment will be given by;

 = (0.7-0.67)/0.7 × 100

 = 0.03/0.7 × 100

= 4.29%

that would be given by

f=@N

@ representing coefficient of kinetic friction.

thus 19.5/51.7 = 0.377

Answer:

the process whereby organisms better adapted to their environment tend to survive and produce more offspring. The theory of its action was first fully expounded by Charles Darwin and is now believed to be the main process that brings about evolution.

Explanation:

Answer:Density-independent factors, such as weather and climate, exert their influences on population size regardless of the population's density. In contrast, the effects of density-dependent factors intensify as the population increases in size.

Explanation:

Answer:

Density independent.

Explanation:

Many factors which are physical or chemical in nature can influence the mortality of a population. They are occur by the inclusion of weather, natural disaster and pollution. A deer may be died in a forest due to fire and its chances of survival depends on the quantity of population density whether its high or low.

Density independent regulation can be affected by the various factors that affects the death rate or birth rates such as environmental factor and abiotic factors.

0N. The net force acting on this firework is 0.

The key to solve this problem is using the net force formula based on the diagram shown in the image. Fnet = F1 + F2.....Fn.

Based on the free-body diagram, we have:

The force of gases is Fgases = 9,452N

The force of the rocket Frocket = -9452

Then, the net force acting is:

Fnet = Fgases + Frocket

Fnet = 9,452N - 9,452N = 0N

Based on the free-body diagram, the net force acting on this firework is 0 Newton.

Newton's Second Law states that The resultant force acting on an object is proportional to the rate of change of momentum.

The mathematical expression for Newton's second law is as follows

F = m*a

where F represents the force applied

m is the mass of the object

a is the acceleration of the object

By using the equilibrium of the forces

The net horizontal forces acting on the firework should be zero.

as well the net vertical forces acting on the firework should be zero.

As there is no horizontal force acting on the rocket then the net horizontal force is already zero and has no significance in this problem.

Fh=0

For balancing the vertical force, the net vertical force on the firework is zero as both the upward force and downward force are equal in magnitude but opposite in direction.

Net vertical force= Net upward force - net downward force

                             = 9452-9452

                             =0 N

Thus, we can conclude on the basis of the free-body diagram, that the net force acting on this firework is 0 Newton.

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It is also known as iteration. It is used mostly in computer programming with for and for each loops in which iteration is present. In mathematics there are some "interational operations" like product and sum for eg:

[tex]

J=\sum_{i=1}^{n}J_i\Longrightarrow J_1+J_2+\dots+J_{\infty}

[/tex]

The above equation describes the summation of J alike variables n times.