Answer: Rotation cause by the earths orbit and gravity
Explanation:
Answer: Crystals are formed by the earth and the earth itself otherwise then its a fake crystal
Explanation:
Every crystal that exists was formed when earth was formed. Take diamonds for example, All diamonds were crushed for millions of years by the earth and that's why they are so valuable. All diamonds are just coal.
So your answer is no but fake crystals yes
Answer:
The kinetic energy of the two stones is 320 J
Explanation:
Kinetic energy is the energy that a body possesses due to its movement. So it is the capacity or work that allows an object to go from being at rest, or still, to moving at a certain speed.
In other words, the kinetic energy of an object is that which is produced due to its motion and depends on its mass and velocity as follows:

where the kinetic energy Ec is measured in joules (J), the mass m is measured in kilograms (kg) and the velocity v in meters/second (m/s).
In this case you know that a 20 kg curling stone is sliding in a positive direction at 4 m/s. So:
Replacing you have:

Ec₁= 160 J
A second curling stone slides at the same speed but in the opposite direction. So:
Replacing you have:

Ec₂= 160 J
The kinetic energy of the two stones is calculated as:
Ec= Ec₁ + Ec₂
Ec= 160 J + 160 J
Ec= 320 J
<u><em>The kinetic energy of the two stones is 320 J</em></u>