Explanation:
The volume of a simple compressible system is not fixed. At a state of equilibrium, there should be uniformity in the entire system.
From the question we have here, these are the correct options:
1. It cannot be a mixture of different substances (e.g. oxygen and nitrogent)
2. It can be composed of any phases of a substance: solid, liquid, and/or gas
3. It's state is specified if given two independent, intensive thermodynamic properties.
Answer:

Explanation:
Given:
Thickness of the paperweight cube, 
apparent depth from one side of the inbuilt paper in the plastic cube, 
apparent depth from the other side of the inbuilt paper in the plastic cube, 
Now as we know that refractive index is given as:

- Let the real depth form first side of the slab be,

- Then the depth from the second side of the slab will be,

Since refractive index for an amorphous solid is an isotropic quantity so it remains same in all the direction for this plastic.




Now the refractive index:



The net force on an object subject to friction is equal to the sum of the applied force and the frictional force.
Mathematically,

Here, m is mass of object and a is its acceleration. We take frictional force negative because it opposes the motion of object.
Given,
,
and 
Substituting these values in above formula, we get
.
Thus, the acceleration of an object is 
Answer:
15 to 30 so anywhere in between there.
Answer:
Two factors effecting the magnitude of the force of gravity between 2 objects are the product of their masses and square of distance between them.
Explanation:
According to Newton's law of universal gravitation

where F is the gravitational force, G is the universal gravitational constant and its value is 6.6743 × 10⁻¹¹ Nm²/kg₂ , m₁ and m₂ are masses of bodies and r is the distance between them.
It can be seen from the above equation that F is directly proportional to the product of the masses and inversely proportional to the square of distance between them.
F ∝ m₁m₂
F ∝ 1/r²
As far as the masses of the bodies increase, magnitude of the Gravitational force increases and if distance between them increase then Gravitational force between them decreases.