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2 years ago

_______________ involves removing the top layer of earth, mining the coal, and then replacing the earth back on the surface

1 answer:

5 0

Surface mining is the method of removing the overburden parts of the earth which are the earth and rocks. It also involves removal and loading out of the coal, and then placing back the collected earth back into a surface once again. It's also a method that uses equipment or explosives.

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If the object is released from rest at point p,what is the kinetic energy at the lowest point Q of its swing.

marta [7]

Answer:

50%

Explanation:

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3 years ago

A star is estimated to be 4.8 x 10^15 kilometers away from the earth. When we see this star in the night sky, how old is this im

Veseljchak [2.6K]

Answer:

B. 500 years

Explanation:

The light coming from the star and reaching us on the Earth travels with uniform motion (with constant velocity), so we can use the equation of uniform motion which relates distance covered, speed and time taken:

$v=\frac{d}{t}$

where

v is the speed

d is the distance covered

t is the time taken

In this problem:

$v=3.00\cdot 10^8 m/s$ is the speed at which light travels

$d=4.8\cdot 10^{15} km = 4.8\cdot 10^{18}m$ is the distance that light has to cover from the star to the Earth

Therefore, by rearranging the equation, we can find the time:

$t=\frac{d}{v}=\frac{4.8\cdot 10^{18}}{3.00\cdot 10^8}=1.6\cdot 10^{10}s$

And by converting into years, this time is

$t=\frac{1.6\cdot 10^{10}}{(365)(24)(60)(60)}=507 y$

So, approximately 500 years: this means that the image we see of the star is 500 years old.

4 0

2 years ago

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How many laws of Newton and who

nasty-shy [4]

Answer:

The three laws of motion were first compiled by Isaac Newton in his Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), first published in 1687. Newton used them to explain and investigate the motion of many physical objects and systems

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2 years ago

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atmospheric pressure is measured in all of the following units except ……… ? A. torr B. pascal C. bar D. newton?

AlexFokin [52]

Answer:

C. Bar

Explanation:

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1 year ago

What is the princple behind electric generator

Liula [17]

Look, according to newton’s law of the conservation of mass power, the principle behind the electric generator would be when a conductor is moved in a magnetic field than the current is moved buh the conductor

4 0

3 years ago