How did pinkish white skin evolve from dark skinned populations?

1-2 sentences

many answers to this question so chose whatever you link:

- urbanisation -> more people, humanity keeps on living, more job opportunities etc

- source of income for farmers

- source for food (farming)

- source for trees (eg, to create wood (houses), or to use logs for fire)

Answer:

See below

Explanation:

F = ma

  = 85 * 9.8 = 833 N

OR this could be written as 187.4 pounds

    OR   187 kg-weight     (not just kg)

85 kg is a measure of MASS, but is often (though improperly) used as weight on earth.

Answer:

The contribution of the wavelets lying on the back of the wave front is zero because of something known as the Obliquity Factor. It is assumed that the amplitude of the secondary wavelets is not independent of the direction of propagation, Sources: byju's.com

According to the Voigt and Kirchhoff's law for wavelets, the contribution of a wavelet in any direction making an angle x with the normal to the wavelet is proportional to {1+cos(x)/2)}

For wavelet lying on the back of secondary wavefront,

→ So, the proportional factor:

→ {1+cos(180°)/2}

→ (1-1/2)

→ (0/2)

→ 0

That's why the contribution of the wavelets lying on the back of secondary wave front is zero

The acceleration of the car will be 2m/s².Option A is correct. According to Newton's second law, the eventual effect of all forces applied to a body is its acceleration.

The rate of change of velocity with respect to time is known as acceleration.

Given data;

Initial velocity,u=10m/s

Final velocity,v=40m/s

Time elapsed,t=15 seconds

To find ;

Acceleration, a

The acceleration when the change in the velocity is observed by the formula as:

[tex]\rm a= \frac{v-u}{t}[/tex]

Substitute the given values:

[tex]\rm a= \frac{40-10}{15} \\\\ a=\frac{30}{15} \\\\ a=2 \ m/s^2[/tex]

The car's acceleration will be 2 m/s².

Hence, option A is correct.

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Answer:

Hope this helps!

Explanation:

The seeds are removed for two reasons:

- You cannot spin cotton into a yarn if there are seeds still in the cotton.

- The seeds are a very valuable component of cotton and have a variety of uses.

Answer:

True

Explanation:

hope it will help you

The  work required to assemble this charge arrangement starting with each of the charges as very large distance from any of the other charges is +1.9 J.

The work required to assemble this charge arrangement starting with each of the charges as very large distance from any of the other charges is calculated as follows;

W = qV

where;

[tex]W = q (\frac{kq}{r} )[/tex]

where;

[tex]W = q (\frac{kq}{r} + \frac{kq}{r\sqrt{2} } + \frac{kq}{r} )\\\\W = \frac{kq^2}{r} ( 2 + \frac{1}{\sqrt{2} } )\\\\W = \frac{(9\times 10^9 \times (4\times 10^{-6})^2}{0.2} ( 2.707)\\\\W = 1.9 \ J[/tex]

Thus, the  work required to assemble this charge arrangement starting with each of the charges as very large distance from any of the other charges is +1.9 J.

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What will most likely lead a scientist to investigate a blood-thinning agent in the saliva of vampire bats is curiosity.

Curiosity is defined as an inquisitive trait which is one of the qualities of a good scientist which drives them to discover more in their field.

For a scientist to investigate a blood-thinning agent in the saliva of vampire bats would have been driven by curiosity to do so.

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Explanation:

The comparison of an unknown physical quantity with the known standard quantity is called measurement....

Here are some tho.....

Answer: 1600 km from the surface

Explanation:

[tex]E = \frac{GM}{R^{2} }\\g1 = \frac{GM}{R1^{2} } \\R1 = 6400 km\\g2 = 0.64g1\\\frac{g1}{g2} = \frac{\frac{GM}{R1^{2} } }{\frac{GM}{R2^{2} } } \\\frac{g1}{0.64g1} = \frac{R2^{2}}{R1^{2} }\\\frac{1}{0.64} = \frac{R2^{2}}{6400^{2} }\\\\\frac{1}{0.8} = \frac{R2}{6400}\\\\R2 = \frac{6400}{0.8}\\R2 = 8000 km\\[/tex]

Therefore, 8000 km - 6400 km = 1600 km from the surface

If the weight of the metal disk is 1.0 N, the normal force acting on the metal disk is also 1.0 N but acting in the opposite direction.

According to Newton Law, action and reaction are equal and opposite. The reaction force is equal in magnitude to the weight of an object but opposite in direction.

Having said that, if the weight of the metal disk is 1.0 N, the normal force acting on the metal disk is also 1.0 N but acting in the opposite direction.

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The power dissipated by the LED is 20 Watts and the work done for 1 hour 15 minutes is 56.25 kJ.

Electrical power is the rate at which electrical work is done.

The LED is 75% efficient means that 75% of power dissipated by the LED is converted to light.

Total power dissipated = 5 × 2.5 = 12.5 Watts

Work done = 12.5 × (1 × 3600 + 15 × 60)

Work done = 56250 J = 56.25 kJ

Therefore, the power dissipated by the LED is 20 Watts and the work done for 1 hour 15 minutes is 56.25 kJ.

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The displacement of Edward in the westerly direction is determined as 338.32 km.

The displacement of Edward can be determined from different methods of vector addition. The method applied here is triangular method.

The angle between the 200 km north west and 150 km west = 60 + 90 = 150⁰

The displacement is the side of the triangle facing 150⁰ = R

R² = a² + b² - 2abcosR

R² = 150² + 200²  - (2x 150 x 200)xcos(150)

R² = 62,500 - (-51,961.52)

R² = 114,461.52

R = 338.32 km

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From the calculation , we can see that the specific heat capacity is 513 kJ

The specific heat capacity is the heat that can be able to raise the temperature of 1 Kg of a material by 1K.

Now;

We know that;

Latent heat of evaporation = 855kJ/kg

Mass of the liquid = 0.60kg

H = mL

H = 0.60kg * 855kJ/kg

H = 513 kJ

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Answer:

X-rays are commonly produced in X-ray tubes by accelerating electrons through a potential difference (a voltage drop) and directing them onto a target material 

Answer:

Mitosis

Explanation:

Mitosis is a process of nuclear division in eukaryotic cells that occurs when a parent cell divides to produce two identical daughter cells. During cell division, mitosis refers specifically to the separation of the duplicated genetic material carried in the nucleus.

The components of the net force on the cart is determined as 67.66 N.

The component of net force on the cart is determined by resolving the forces into x and y -components.

T1 = 30 N

T2 = 40 N

T1x = -30cos(0) = 30 N

T1y = 30sin(0) = 0

T2x = 40 x cos(30) = 34.64 N

T2y = 40 x sin(3) = 20 N

∑X = 30 N + 34.64 N = 64.64 N

∑Y = 0 + 20 N = 20 N

R = √(64.64² + 20²)

R = 67.66 N

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Answer:

The proton has much greater mass

Explanation:

Answer:

D, a proton has a much greater mass.

Explanation:

An electron has a mass close to nothing.

Given the work done, the force exerted on the taco stand through the given distance is 2.3 × 10³ Newtons.

Work done is simply defined as the energy transfer that takes place when an object is either pushed or pulled over a certain distance by an external force. It is expressed as;

W = f × d

Where f is force applied and d is distance travelled.

Given that;

W = f × d

3500kgm²/s² = f × 1.5m

f = 3500kgm²/s² ÷ 1.5m

f = 2.3 × 10³ kgm/s²

f = 2.3 × 10³ N

Given the work done, the force exerted on the taco stand through the given distance is 2.3 × 10³ Newtons.

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Voltage is always twice the amount of power. This is statement is accurately describe the relationship between voltage and electric power.

Power is defined as amount of energy transferred or converted per unit time.

From power-current relation

P=VI

Also, From Ohm's Law we know that,

V= IR

Replacing the value of V in the above equation,

[tex]P =\frac{I^{2} }{R}[/tex]

When the values for current and resistance are given then the equation is,

[tex]P =\frac{V^{2} }{R}[/tex]

Hence , Voltage is twice to the electric Power.

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Answer:

some people failed to realize that the earth is round ligit

Explanation: they failed to do that because of how our eyes see the earth so they was like okay it is flat caused the never saw a person that showed it on the internet

Answer: 100,000 Pa

Explanation:

[tex]$$Applied Force $=200 \mathrm{~N}$ \\Area $=0.002 \mathrm{~m}^{2}$\\\\Pressure $=\frac{\text { Force }}{\text { Area }}$\\$=\frac{200}{0.002}$\\$=\frac{200}{2 \times 10^{-3}}$\\$=100,000 \mathrm{~Pa}$[/tex]

One problem with digital data is that it can be vulnerable to hackers. A Hacker is a person who gains unauthorized access to digital data. Thus, Option C is the correct answer.

The word Hacker usually refers to a person who will uses computer to access individually to overcome the technical issues. Not only technical problem some person also use the computer to involve in the unauthorized  data for the process of criminal behaviors.

They will make the data or information to get deleted and also steal or change the data in an unauthorized way.

Thus, if there was a problem with digital data is that it can be vulnerable then a person who gains unauthorized access to digital data is known as Hacker.

So, Option C is the correct answer.

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Answer:

O C. A person who gains unauthorized access to digital data

Explanation:

(a) The projectile's velocity at the highest point of its trajectory is 51.96 m/s.

(b) The maximum height reached by the projectile is 45.92 m.

At the highest point of trajectory the vertical component of the velocity will be zero will the horizontal component will remain constant.

Vxi = Vxf = Vcosθ = 60 x cos30 = 51.96 m/s

The maximum height reached by the projectile is calculated as follows;

H = u²sin²θ/2g

H = (60² x (sin30)²)/(2 x 9.8)

H = 45.92 m

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Answer:

4.9

Explanation:

Velocity half second before maximum height = Velocity half second after maximum height (Return journey)

For downward journey :

Initial velocity u=0 m/s

We have g=9.8 m/s

Time t= ½s

s

Thus velocity after half second v=u+gt

v=0+9.8× ½ =4.9m/s

Answer:

True, the total amount of mechanical energy is merely the sum of the potential energy and the kinetic energy. This sum is simply referred to as the total mechanical energy.

Explanation: Hope it helps you:))))

have a good day

Answer:

All of the above

Explanation:

hope it helps you

Congo/Zaire region is the country which experienced chaos after their independence due to lack of experience in democratic self-government.

This type of government involves the people making legislative decisions and choosing those who will rule and represent them.

Congo/Zaire region was not self sufficient and were inexperienced in democratic self-government after independence which led to political crisis.

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All the statements are correct for the strength of electric field.

The amount of charge on the source and the distances from the source charge both affect how strong the electric field is.

All the statements are true as

The electric force varies directly with charge therefore , statement 2 is correct

The electric force varies indirectly with the distance between the electric field , Therefore statement 1 is correct.

It is known that Oppositely charged objects will attract each other , Statement 3 is correct.

Therefore all the statements are correct for the strength of electric field.

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The light of the second laser compare with the original laser in the following way: the light in the second laser absorbs more optical radiation.

A laser is device that produces a monochromatic, coherent beam of light.

A laser is created when electrons in the atoms in optical materials like glass, crystal, or gas absorb the energy from an electrical current or a light.

Therefore, it can be said that light of the second laser compare with the original laser in the following way: the light in the second laser absorbs more optical radiation.

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