Answer:
D. are brought from the mantle to the surface in magma that hardens into komatiite.
Explanation:
Diamond :
It is the hardest form of carbon.The atomic atoms arrange in the cubic crystal structure and this is known as diamond cubic.Another form of the diamond at room temperature is graphite.This is used for making jewelry.This is also used in the cutting process because it has high strength.
Therefore the correct option for the diamond is D.
Answer: 
Explanation:
We are told both planets describe a circular orbit around the star S. So, let's approach this problem begining with the angular velocity
of the planet P1 with a period
:
(1)
Where:
is the velocity of planet P1
is the radius of the orbit of planet P1
Finding
:
(2)
(3)
(4)
On the other hand, we know the gravitational force
between the star S with mass
and the planet P1 with mass
is:
(5)
Where
is the Gravitational Constant and its value is 
In addition, the centripetal force
exerted on the planet is:
(6)
Assuming this system is in equilibrium:
(7)
Substituting (5) and (6) in (7):
(8)
Finding
:
(9)
(10)
Finally:
(11) This is the mass of the star S
Over time, the substances will reach equilibrium, meaning the heat calories lost by Substance 1 will be gained by Substance 2. Therefore, Substance 2 will eventually gain 40 calories of heat.
Work is done when spring is extended or compressed. Elastic potential energy is stored in the spring. Provided inelastic deformation has not happened, the work done is equal to the elastic potential energy stored.
The correct options are: B, C and D.
In fact:
- B is true, because the motion of the projectile can be decomposed in two independent motions on the x and y axis. On the x-axis, there is no acceleration; while on the y-axis, the projectile is accelerating towards the ground with

(acceleration of gravity)
- C is true, because the two motions on the horizontal and vertical direction are independent. In particular, the horizontal motion is a uniform motion (constant velocity), while the vertical motion is a uniformly accelerated motion (because of the gravitational acceleration g acting on the projectile)
- D is true, in fact (if we neglect air resistance) gravity is the only force acting on the projectile.