What would most likely occur if the number of power plants powered by fossil
fuels worldwide increased?

A. It would lower the amount of carbon dioxide in the atmosphere
because less coal would be burned.
B. It would lower the amount of carbon dioxide in the atmosphere
because more natural gas would be burned.
C. It would cause the amount of carbon dioxide in the atmosphere to
increase because more coal would be burned.
D. It would cause the amount of carbon dioxide in the atmosphere to
increase because less natural gas would be burned.

Answer:

D

Explanation:

Diamond, graphite and fullerenes (substances that include nanotubes and 'buckyballs' , such as buckminsterfullerene) are three allotropes of pure carbon. In all three allotropes, the carbon atoms are joined by strong covalent bonds, but in such different arrangements that the properties of the allotropes are very different.

Because of their distinctive structural makeup, graphite and diamond are distinct materials. Both have extremely high melting points due to their giant covalent structures. Diamond is incredibly strong and hard due to the four covalent links that each carbon atom in the mineral has with other carbon atoms. However, because each carbon in graphite is connected to three other carbons, it forms in layers.

Even though graphite is used to make pencils, despite the fact that each carbon atom only has three bonds, the layers are actually highly strong and have delocalized "free" electrons between them. Graphite appears soft because these electrons act as a lubricant between layers, allowing them to slide over one another. Graphite conducts electricity due to the free electrons. Diamond does not carry electricity because it lacks these free electrons.

There are more than three allotropes of carbon. These include diamond, graphite, graphene, carbon nanotubes, fullerenes, and carbon nanobuds.

Diamond

In a three-dimensional array, four additional carbon atoms are covalently attached to each carbon atom in a diamond. In essence, a diamond is one enormous molecule.

Graphite

The carbon atoms in graphite are bonded together in sheets of connected hexagons that resemble chicken wire. In essence, each sheet is a single molecule.

Each carbon atom in a sheet establishes solid covalent bonds with three other carbon atoms. The only forces keeping the sheets packed together are the modest intramolecular forces.

Graphene

In the form of a single sheet of graphite that is only one atom thick, graphene is made up entirely of carbon.

Nanocarbon tubes

Graphene sheet wrapped into a cylindrical tube of carbon atoms is how a carbon nanotube looks. Each atom connected to three other atoms, and the tube is one atom thick.

C60 and buckminsterfullerene

A single sheet of carbon atoms that has been folded into a spherical is what makes up buckminsterfullerene. Three additional atoms are connected to each carbon atom. With a carbon atom at each of the 20 hexagonal and 12 pentagonal corners, sixty carbon atoms are arranged in the shape of a ball.

There are numerous other known carbon balls, such as C70, C76, C84, and C540. They are collectively referred to as "buckyballs" or "fullerenes" and have varying amounts of pentagons and hexagons.

Nanocarbon buds

An allotrope of carbon called carbon nanobuds has fullerene-like "buds" that are covalently bonded to the sidewalls of carbon nanotubes.

To learn more about the allotropes of carbon please click on the link https://brainly.com/question/20897327

#SPJ9

Answer:

Hope this is helpful!

Explanation:

In every form of collision the momentum is conserved and it is the same before and after the collision, but in perfectly elastic collision, there is no loss of kinetic energy in the collision. In an inelastic collision is one in which part of the kinetic energy is changed to some other form of energy in the collision. Any macroscopic collision between objects will convert some of the kinetic energy into internal energy and other forms of energy.

Answer:

To find the height at which the two objects will first meet, we need to use the equations of motion for free fall and vertical upward motion.

The equation for free fall is:

h = h0 + v0t + (1/2)at^2

where h is the height of the object at time t, h0 is the initial height, v0 is the initial velocity (which is zero for free fall), and a is the acceleration due to gravity (which is 9.8 m/s^2 downward).

The equation for vertical upward motion is:

h = h0 + v0t - (1/2)gt^2

where h is the height of the object at time t, h0 is the initial height, v0 is the initial velocity, and g is the acceleration due to gravity (which is 9.8 m/s^2 downward).

We know that the first object is in free fall, and that it began at a height of 22.0 m. We also know that the second object was launched upward with an initial velocity of 32.0 m/s, 1.10 s after the first object was released.

We can use these values to find the height of the first object at the time the second object is launched:

h1 = 22.0 + 0 + (1/2)(-9.8)(1.10^2) = 20.27 m

We can use this value as the initial height for the second object:

h2 = 20.27 + 32.0(1.10) - (1/2)(-9.8)(1.10^2) = 37.47 m

Now we need to find the time at which the two objects will meet. We can use the height of the first object at the time the second object is launched, and the equation for free fall to find the time it takes for the first object to reach the height of the second object:

37.47 = 20.27 + 0 + (1/2)(-9.8)t^2

Solving for t, we find that the objects will meet at a time of approximately 1.47 seconds.

Finally, we can use this time to find the height at which they will meet:

h = 22.0 + 0 + (1/2)(-9.8)(1.47^2) = 37.47 m

So the objects will first meet at a height of 37.47 m above the ground.

Answer: Density = 6071.428571 kg/m³

Explanation: Given that mass m=17 kg

volume displaced v=2.8L

We know that

density = mass/volume

Here density=17kg/2.8L

Also 1L=1000m³ Hence

density=17kg/2.8×10⁻³m³

           =6071.428571 kg/m³

Answer:

-48cm

Explanation:

For a convex lens f is +ve and V is +ve

Using the formula 1/f=1/v+1/u

u=12cm and f=16cm

1/16-1/12=1/v

1/v=-1/48

v=-48cm

Answer:

Tension in the string provides the centripetal force. A tether ball is tied to a string and whirled in a horizontal circular path at a constant speed.

Explanation:

Answer:

the answers the correct one is cη

Explanation:

In this simple pendulum experiment the student observes a significant change in time between each period. This occurs since an approximation used is that the sine of the angle is small, so

              sin θ = θ

with this approach the equation will be surveyed

     d² θ / dt² = - g / L sin θ

It is reduced to

      d² θ / dt² = - g / L θ

in which the time for each oscillation is constant, for this approximation the angle must be less than 10º so that the difference between the sine and the angles is less than 1%

The angle is related to the height of the pendulum

         sin θ = h / L

         h = L sin θ.

Therefore the student must be careful that the height is small.

When reviewing the answers the correct one is cη

Considering the approximation of simple harmonic motion, the correct option is:

(c) Make sure that the difference in height between the pendulum's release position and rest position is not too large.

According to Newton's second law in case of rotational motion, we have;

\(\tau = I \alpha\)

Applying this, in the case of a simple pendulum, we get;

\(-mg\,sin\,\theta =mL^2 \,\frac{d^2 \theta}{dt^2}\)

On, rearranging the above equation, we get;

\(mL^2 \,\frac{d^2 \theta}{dt^2} + mg\,sin\,\theta=0\\\\\implies \frac{d^2 \theta}{dt^2} +\frac{g}{L} sin \,\theta=0\)

Now, if angular displacement is very small, i.e.; the bob of the pendulum is only raised slightly.

Then, \(sin\, \theta \approx \theta\)

\(\implies \frac{d^2 \theta}{dt^2} +\frac{g}{L} \,\theta=0\)

This is now in the form of the equation of a simple harmonic motion.

\(\frac{d^2 \theta}{dt^2} +\omega^2 \,\theta=0\)

Comparing both these equations, we can say that;

\(\omega = \sqrt{\frac{g}{L}}\)

\(T=2\pi\sqrt{\frac{L}{g}}\)

This relation for the time period can only be obtained if the angular displacement is very less.

So, the correct option is;

Option (c): Make sure that the difference in height between the pendulum's release position and rest position is not too large.

Learn more about simple harmonic motion here:

https://brainly.com/question/26114128

Answer:

Car 1

Characteristic

Car mass

Crumple zone length

1,450 kg

110 cm

Explanation:

///

Answer:

Explanation:

The spring stiffness is quantified by the spring constant, or k. For various springs and materials, it varies.

The stiffer the spring is and the harder it is to stretch, the larger the spring constant.

Springs are pliable mechanical devices that regain their previous shape after deforming, i.e. after being stretched or compressed. They are an essential part of many different mechanical devices.

The well-known metal coil has evolved into an essential element in the modern world, appearing in everything from engines to appliances to tools to automobiles to medical equipment and even basic ball-point pens. The spring's ability to store mechanical energy accounts for its widespread use and applications.

Therefore, The spring stiffness is quantified by the spring constant, or k. For various springs and materials, it varies.

To learn more about Spring constant, refer to the link:

https://brainly.com/question/29975736

#SPJ1

Hello..! :)

The speed of the ancient ship is 3482 meters per hour or 96.72 centimeters per second.

Explanation:

Data:

Formula:

Developing:

Now, we convert to see what its speed is in cm/s.

Conversion:

V = 96.72 cm/s

¿Doubts? On the comments. Greetings :D

Answer:

Thanks For the points

It is or 96.72 cm/s

The car is moving at approximately 12.5 meters per second.

The kinetic energy (KE) of an object can be calculated using the formula:

KE = 1/2 * m * \(v^2\)

where

KE = kinetic energy,

m =Mass of the object, and

v = velocity.

In this case, we are given the mass (m) of the car as 1600 kg and the kinetic energy (KE) as 125,000 J. To find the velocity .

Substituting the  values , we have:

125,000 J = 1/2 * 1600 kg *\(v^2\)

Now, we can solve for v by rearranging the equation:

\(v^2\) = (2 * 125,000 J) / 1600 kg

\(v^2\) = 156.25 \(m^2/s^2\)

Taking the square root, we find:

v = √156.25\(m^2/s^2\)

v ≈ 12.5 m/s

Therefore, the car is moving at approximately 12.5 meters per second.

Know more about   kinetic energy  here:

https://brainly.com/question/8101588

#SPJ8

Answer:

Two major muscles must work together in an agonist and antagonist form to be able to move an arm.

Explanation:

Answer:

A) When the insect starts to fall.

Assuming that the little insect can not do anything (he/she does not have wings or anything like that) the only force acting on the insect will be:

Gravitational force: Is the force that pulls down the insect.

Air resistance: As the insect starts to move, the air will try to oppose to that motion.

B) When the insect falls at a constant speed.

This will happen when the air resistance equals in magnitude (but in opposite direction) the gravitational force.

Now the net force is zero, so the insect is not accelerated anymore, which means that the insect moves at a constant speed.

And the fact that the net force is zero does not mean that the gravitational force and the air resistance are "not acting" on the insect, this means that those forces are not having any effect in the dynamics of the insect's motion.

C) When it lands.

When the insect lands, there is a new force that appears, the normal force of the ground that opposes to the movement of the insect through it.

As the insect comes to stop (because he hits the ground) the air resistance does not longer act on it, so now the normal force of the ground is equal in magnitude (but in opposite direction) to the gravitational force, then the net force is zero.

D) When is there a net force acting and in what direction?

The only time that is a net force acting, is when the insect starts to fall, where the gravitational force is accelerating the insect downwards.

E) What force pair is there when the insect lands?

The force pair is the gravitational force, and the reaction, the normal force of the ground.

Answer:

Explanation:

Step one:

given data

mass m= 300kg

applied force F= 1000N

coefficient of friction μ= 0.3

Step two:

The net force Fn= applied force-friction force  

Fn=F-F1

F1= limiting force

F1=μ*m*g

F1=0.3*300*9.81

F1=882.9N

the Net force= 1000-882.9

Fn=117.1N

Step three:

we know that

F=ma

Fnet=ma

a= Fnet/m

a=117.1/300

a=0.39m/s^2

Gary's weight at 300 km above Earth's surface is 91% of his weight at the surface.

The Earth's surface is a living union of its solid crust, atmosphere, hydrosphere, and biosphere, all of which have worked together to create a continually regenerating and dynamic symphony of form. From the Solar System Encyclopedia.

It has a substantial and dynamic surface with mountains, valleys, canyons, plains, and a variety of other features. Earth is unique in that it is an ocean world. 70% of the Earth's surface is covered by water. The Earth's atmosphere is mainly nitrogen, with enough of oxygen for humans to breathe.

a) The mass of an object is an intrinsic attribute, which means that it is determined only by the qualities of the thing and is not affected by its position. As a result, Gary's mass at 300 kilometers above the Earth's surface equals his mass at the Earth's surface.

b) The weight of an object is given by, W = mg

where

m is the mass and g = GM /r²

It is the gravitational acceleration at the location of the object, with G being the gravitational constant, M the mass of the planet and r the distance of the object from the center of the planet.

At the Earth's surface, g = 9.81 m/sec²

so Gary's weight is W = mg

W = 9.81 m  ...........(1)

where m is Gary's mass.

Then, we must calculate the value of g at 300 km above Earth's surface. the Earth's radius is, R = 6370 Km.

So the distance of Gary from the Earth's center is:

r = R + h

r = (6370 +300) Km

r = 6670 km

r = 6.67 × 10⁶ m

The Earth's mass is M = 5.97 × 10²⁴ Kg , so the gravitational acceleration is, g₁ = GM /r²

g₁ = [(6.67 10⁻¹¹ m³ kg⁻¹ s⁻²) × (5.97 × 10²⁴ Kg)] ÷ (6.67 × 10⁶ m)²

g₁ = 8.95 m/sec²

Therefore, Gary's weight at 300 km above Earth's surface is:

W₁ = mg₁

W₁ = 8.95 m  ............(2)

If we compare (1) and (2), we find that Gary's weight has changed by

W₁/W = 8.95 m/ 9.81 m

W₁/W = 0.91

So, Gary's weight at 300 km above Earth's surface is 91% of his weight at the surface.

To know more about earth's surface refer to:

https://brainly.com/question/1406428

#SPJ1

Answer:

good job my boy this is the right answer

Explanation:

The potential energy of the roller coaster is 176,400 J (joules).

The potential energy of an object is given by the formula PE = mgh, where PE is the potential energy, m is the mass of the object, g is the acceleration due to gravity, and h is the height or vertical position of the object.

In this case, the roller coaster is at a peak of 20m and has a mass of 900kg. The acceleration due to gravity, g, is approximately 9.8 \(m/s^2\).

Using the formula, we can calculate the potential energy:

PE = mgh

= (900 kg)(9.8 \(m/s^2\))(20 m)

= 176,400 J

Therefore, the potential energy of the roller coaster is 176,400 J (joules).

Know more about  potential energy    here:

https://brainly.com/question/21175118

#SPJ8

When the thistle funnel is moved upwards towards the surface of the liquids, the height (h) decrease.

What happens when the thistle funnel is moved upward?

An important principle outlined by Pascal's law states that any fluid (in this instance, liquids) experiences equal transmission of force in every direction within it. Hence, there is an intimate relationship between the height of a liquid column and its pressure.

Raising a thistle funnel reduces this height causing loss of weight from above this point thus decreasing its pressure.

Learn about pressure here https://brainly.com/question/30638771

#SPJ1

See complete question in the attached image.

Answer:

4 m

Explanation:

We can represent the standing wave as follows

So, we can divide the total distance into 6 parts as follows

12 m/6 = 2 m

Then, 2 m is the distance from node to node. It means that the wavelength will be twice this distance, so

wavelength = 2 x 2m = 4m

Therefore, the wavelength is 4m

Answer:

A B C

Explanation:just took the test

Answer:

Komal could have mixed up the labels on the vials.

Someone might have jiggled the table and made the water surface tension bubble spill over.

The water could actually have been saltwater instead of pure water.

Explanation:

...........................

Answer:

when you turn down the volume on the television, you reduce the intensity carried by the sound waves, so you also reduce their amplitude.

Explanation:

When you turn down the volume of the television, you are actually reducing the intensity of the sound wave, which is directly proportional to the amplitude of the sound. Amplitude is height of the sound wave.

Therefore, when you turn down the volume on the television, you reduce the intensity carried by the sound waves, so you also reduce their amplitude.

While the Sun's corona is incredibly hot, the combined effects of distance, the vacuum of space, Earth's atmosphere, and the distribution of solar energy help protect us from being incinerated.

The Sun's corona indeed has an extremely high temperature, reaching up to millions of degrees Celsius. However, despite this intense heat, we are not incinerated due to a combination of factors.

Firstly, the corona's high temperature does not directly translate to an increase in heat transfer to objects at a distance from the Sun. Heat transfer occurs through conduction, convection, and radiation, but in the case of the Sun, the distance and vacuum of space act as insulating factors, significantly reducing the amount of heat reaching Earth.

Secondly, Earth's atmosphere plays a crucial role in protecting us from the Sun's extreme temperature. The atmosphere acts as a shield, absorbing and scattering a significant portion of the Sun's radiation. It filters out the most harmful ultraviolet and X-ray radiation, preventing it from reaching the surface.

Additionally, the Sun's energy is emitted in all directions, and only a small fraction reaches Earth. The vastness of space and the Sun's distribution of energy ensure that the Earth receives a manageable amount of solar radiation, which supports life rather than incinerating it.

For such more questions on atmosphere

https://brainly.com/question/3079342

#SPJ11

Answer:

The drop in temperature overnight causes a decrease in the average kinetic energy of the air molecules inside the tires. According to the ideal gas law, this leads to a decrease in tire pressure. The low tire pressure light in vehicles is triggered when the pressure falls below a certain threshold, alerting the driver to check and adjust the tire pressure.

Explanation:

The ideal gas law, represented by the equation PV = nRT, relates the pressure (P), volume (V), number of moles (n), and temperature (T) of an ideal gas. In this case, we can analyze how the drop in temperature affects the tire pressure.

When the temperature drops, according to the ideal gas law, the pressure of a gas will decrease if the volume and the number of moles remain constant. This is because the decrease in temperature causes a decrease in the average kinetic energy of the gas particles, leading to less frequent and less forceful collisions with the tire walls, resulting in a decrease in pressure.

In the context of the tire pressure, the air inside the tires behaves as an ideal gas. When the temperature drops overnight, the air inside the tires also cools down, causing a decrease in its temperature. As a result, the average kinetic energy of the air molecules decreases, leading to a decrease in pressure inside the tires.

The low tire pressure light comes on as a result of this drop in pressure. The tire pressure monitoring system in modern vehicles is designed to detect significant deviations from the recommended tire pressure. When the pressure drops below a certain threshold, typically due to temperature changes or a puncture, the light is triggered to alert the driver to check and adjust the tire pressure.

Therefore, the drop in temperature overnight causes a decrease in the average kinetic energy of the air molecules inside the tires, resulting in a decrease in tire pressure, which triggers the low tire pressure warning light.

Hope this helps!

Answer:

D = 3.81 x 10⁻² m = 3.81 cm

Explanation:

We can use the formula of fringe spacing from Young's Double Slit experiment to answer this question:

\(\Delta x = \frac{\lambda L}{d}\\\)

where,

Δx = distance between two consecutive dark fringes

λ = wavelength of light beam = 5.37 x 10⁻⁷ m

L = Distance between screen and slits = 2.14 m

d = slit separation = 6.03 x 10⁻⁵ m

But, we need the distance between first dark fringe on 1 side to 2nd dark fringe on other side. It means we need twice the distance between two dark fringes:

\(D = 2\Delta x = 2\frac{\lambda L}{d}\\\)

where,

D = distance between first dark fringe on one side and 2nd dark fringe on other side of central maximum = ?

Therefore,

\(D = \frac{(2)(5.37\ x\ 10^{-7} m)(2.14\ m)}{6.03\ x\ 10^{-5}\ m }\)

D = 3.81 x 10⁻² m = 3.81 cm

Answer:

Explanation:

The Spanish flu pandemic of 1918, the deadliest in history, infected an estimated 500 million people worldwide about one-third of the planet’s population and killed an estimated 20 million to 50 million victims, including some 675,000 Americans. The 1918 flu was first observed in Europe, the United States and parts of Asia before swiftly spreading around the world. At the time, there were no effective drugs or vaccines to treat this killer flu strain. Citizens were ordered to wear masks, schools, theaters and businesses were shuttered and bodies piled up in makeshift morgues.

Does this sound familiar?

Its the same thing but with a different name called the Corona virus pandemic the same thing happened in 1918 and now it is happening again in 2020 , but in in 2020 there are far less people infected by the Corona virus as compared to the Spanish flu the numbers approximate around 70 million infected and deaths are around 2 million.

The rapid spread of Spanish flu in the fall of 1918 was at least partially to blame on public health officials unwilling to impose quarantines during wartime. The public health response to the crisis in the United States was further hampered by a severe nursing shortage as thousands of nurses had been deployed to military camps and the front lines. But one of the chief reasons that the Spanish flu claimed so many lives in 1918 was that science simply didn’t have the tools to develop a vaccine for the virus. Microscopes couldn’t even see something as incredibly small as a virus until the 1930s.

That is why the Spanish Flu claimed so many lives in 1918 and the Corona Virus didn't claim that many.

The Corona Virus patients with respect to Spanish Flu patients exponentially decreased because in 2020 we had the specific tools to fight the virus and since mankind was aware when the world engrossed into the pandemic 100 years before the new the risks that it could impose on the world , People started to Quarantine themselves, more nurses/doctors are available rather than in the era of the 19th century.

Mathematically we would say that the exponential growth would be:

\(y=ab^x\)

This is an exponential function, which means as you increase  x , y  increases exponentially, and where a is the initial value and b is the growth factor.

For example:

There are 100,000 cases of Coronavirus when the virus outbroke. If the number of cases doubles every week then how many cases would be there in 10 weeks?

So the solution would be

\(y=ab^x\\y=100000(2)^{10}\\y=102400000\)

Which means people infected with the virus would be approximate 102.5 million. But since this kind of pandemic already broke out in 1918 called the Spanish flu mankind was wise and controlled its growth factor (b) by Quarantining people , shutting down businesses, schools  and implying them to work from home , closing off cafeteria's restaurants for dine in purposes and just allowing take away to reduce human contact, and since 1918 we have more doctors and nurses to treat the infected in 2020 we reduced the outbreak to 70 million in about 10 months other wise it could have been 100 million in just 2.5 months as we can see.

So guys stay indoors just go out if you REALLY need something, avoid meeting others , wear masks and gloves :)

Answer:

The final angular velocity is rev/s is 0.293 rev/s.

Explanation:

Given;

mass of the merry-go-round, m₁ = 120 kg

radius of the merry-go-round, r = 1.8 m

initial angular velocity, ω = 0.4 rev/s

mass of the child, m₂ = 22 kg

Apply the principle of conservation angular momentum to determine the final angular velocity;

\(I_i= I_f\\\\\frac{1}{2} m_1r^2 \omega _i = \frac{1}{2} m_1r^2 \omega _f + m_2r^2 \omega _f\\\\ \frac{1}{2} m_1r^2 \omega _i =( \frac{1}{2} m_1r^2 + m_2r^2 )\omega _f\\\\\omega _f = \frac{ \frac{1}{2} m_1r^2 \omega _i}{\frac{1}{2} m_1r^2 + m_2r^2} \\\\\omega _f = \frac{ \frac{1}{2} m_1 \omega _i}{\frac{1}{2} m_1 + m_2}\\\\\omega _f = \frac{0.5 \ \times \ 120\ kg \ \times \ 0.4\ rev/s}{0.5 \ \times 120\ kg \ \ + \ \ 22 \ kg} \\\\\omega _f = 0.293 \ rev/s\\\)

Therefore, the final angular velocity is rev/s is 0.293 rev/s.

(a) The work done by the applied force is 32.6 J.

(b) The work done by gravity on the block is 29.4 J.

(c) The magnitude of the normal force is 29.4 N.

The force applied to the block is determined by applying the formula for the net force on the block.

F(net) = 0

Fcosθ - mg - Fsinθμ = 0

Fcosθ - Fsinθμ = mg

F(cosθ - sinθμ) = mg

F = (mg) / (cosθ - sinθμ)

F = (3 x 9.8) / (cos26  -  0.2 x sin26)

F = 36.25 N

The work done by the applied force is calculated as;

W = Fd cosθ

W = (36.25 x 1) x cos(26)

W = 32.6 J

The work done by gravity on the block is calculated as follows;

W = mgd

W = 3 x 9.8 x 1

W = 29.4 J

The magnitude of the normal force is calculated as follows;

N = mg

N = 3 x 9.8

N = 29.4 N

Learn more about normal force here: https://brainly.com/question/14486416

#SPJ1

A set of coordinates on a map grid are called coordinate grid or grid squares.

The quadrants in which ordered pairings, or coordinates, are established typically have two or more intersecting lines. Coordinates are also used in maps.

Eastings and Northings, two types of grid lines, are what make up the grid squares you see on maps. Both Easting and Northing grid lines are numbered from west to east and from south to north, respectively. The vertical lines that separate the map's west and east halves are known as eastings.

GPS coordinates, which are frequently stated in alphanumeric characters, can be used to uniquely identify a specific geographic place on the planet. In this context, coordinates refer to the points where a grid system intersects. Typically, GPS coordinates are written as a combination of latitude and longitude.

To know about map grid

https://brainly.com/question/4955060

#SPJ1