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algol [13]
3 years ago
9

Mining would be classified as a _____ human activity for the environment. Positive or negative

Physics
2 answers:
KATRIN_1 [288]3 years ago
6 0
Positive in sense that we get resources
negative in sense environment gets dirty negative maybe
maxonik [38]3 years ago
3 0

Answer:

do human activity for the

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Question 30
stellarik [79]

Answer: 0.69\°

Explanation:

The angular diameter \delta of a spherical object is given by the following formula:

\delta=2 sin^{-1}(\frac{d}{2D})

Where:

d=16 m is the actual diameter

D=1338 m is the distance to the spherical object

Hence:

\delta=2 sin^{-1}(\frac{16 m}{2(1338 m)})

\delta=0.685\° \approx 0.69\° This is the angular diameter

3 0
3 years ago
2 ways to change frictional force between 2 objects
Zanzabum
In order to change the frictional force between two solid surfaces, it can be changed by shorter distances and by the amount of weight it has or the amount of force that is pushing that object to go however distance it can. 
5 0
3 years ago
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What element is found in liver and is needed to prevent anemia or tired blood
mel-nik [20]
Iron, and lack of red blood cells can cause anemia so you'd need those to prevent it.
6 0
3 years ago
Why do atoms like carbon and nitrogen not like to make ions, while sodium and chlorine do?
KATRIN_1 [288]
The chemical behavior of atoms is best understood in terms of the degree to which an atom of a particular element attracts electrons, a characteristic officially known as electronegativity. When electronegativity is either very high (as in a chlorine atom) or very low (as in a sodium atom) then you have an atom which tends to either acquire or get rid of one or more electrons, and when it does so it becomes an ion. Carbon has a moderate electronegativity and therefore it is more likely to share electrons (forming covalent bonds) rather than either giving them up or acquiring them (forming ionic bonds). Nitrogen does have a relatively high electronegativity and does form ionic bonds, but in ionic compounds it is most often found in the nitrate radical, combined with 3 oxygen atoms. Nitrogen is also found in molecules that have covalent bonds, such as proteins, but it is the moderating influence of carbon that makes this happen.

I should add that inert elements such as helium do not attract electrons but neither do they give up the ones that they have; they are in a special category, and they form no bonds, neither ionic nor covalent.
6 0
3 years ago
During a test, a NATO surveillance radar system, operating at 37 GHz at 182 kW of power, attempts to detect an incoming stealth
Marta_Voda [28]

(a) 2.68\cdot 10^{-6} W/m^2

The intensity of an electromagnetic wave is given by

I=\frac{P}{A}

where

P is the power

A is the area of the surface considered

For the waves in the problem,

P=182 kW = 1.82\cdot 10^5 W is the power

The area is a hemisphere of radius

r=104 km=1.04\cdot 10^5 m

so

A=2\pi r^2=2\pi (1.04\cdot 10^5 m)^2=6.8\cdot 10^{10} m^2

So, the intensity is

I=\frac{1.82\cdot 10^5 W}{6.8\cdot 10^{10}m^2}=2.68\cdot 10^{-6} W/m^2

(b) 5.9\cdot 10^{-7} W

In this case, the area of the reflection is

A=0.22 m^2

So, if we use the intensity of the wave that we found previously, we can calculate the power of the aircraft's reflection using the same formula:

P=IA=(2.68\cdot 10^{-6} W/m^2)(0.22 m^2)=5.9\cdot 10^{-7} W

(c) 8.7\cdot 10^{-18} W/m^2

We said that the power of the waves reflected by the aircraft is

P=5.9\cdot 10^{-7} W

If we assume that the reflected waves also propagate over a hemisphere of radius

r=104 km=1.04\cdot 10^5 m

which has an area of

A=2\pi r^2=2\pi (1.04\cdot 10^5 m)^2=6.8\cdot 10^{10} m^2

Then the intensity of the reflected waves at the radar site will be

I=\frac{P}{A}=\frac{5.9\cdot 10^{-7} W}{6.8\cdot 10^{10} m^2}=8.7\cdot 10^{-18} W/m^2

(d) 8.1\cdot 10^{-8} V/m

The intensity of a wave is related to the maximum value of the electric field by

I=\frac{1}{2}c\epsilon_0 E_0^2

where

c is the speed of light

\epsilon_0 is the vacuum permittivity

E_0 is the maximum value of the electric field vector

Solving the equation for E_0,

E_0=\sqrt{\frac{2I}{c\epsilon_0}}=\sqrt{\frac{2(8.7\cdot 10^{-18} W/m^2)}{(3\cdot 10^8 m/s)(8.85\cdot 10^{-12} F/m)}}=8.1\cdot 10^{-8} V/m

(e) 1.9\cdot 10^{-16} T

The maximum value of the magnetic field vector is given by

B_0 = \frac{E_0}{c}

Substituting the values,

B_0 = \frac{(8.1\cdot 10^{-8} V/m)}{3\cdot 10^8 m/s}=2.7\cdot 10^{-16} T

And the rms value of the magnetic field is given by

B_{rms} = \frac{B_0}{\sqrt{2}}=\frac{2.7\cdot 10^{-16} T}{\sqrt{2}}=1.9\cdot 10^{-16} T

7 0
3 years ago
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