Answer:
Precipitation is the formation of a solid from a solution. It is necessary to centrifuge the precipitate to exert sufficient forces of gravity to bring the solid particles in the solution to come together and settle
Explanation:
When you centrifuge precipitate it enables the nucleation to form.
Centrifuging the precipitate helps in determining whether a certain element is present in a solution or not.
Question 2 is because the passengers have inertia, which is a tendency to resist change in motion
If the object is in equilibrium that means that the sum of the forces on it is zero and the net force is zero. If none of the forces changes then the object continues in constant uniform motion. That means constant speed in a straight line.
Answer:
The chemical formula for the molecule is 
Explanation :
Molecular formula : It is the chemical formula which depicts the actual number of atoms of each element present in the compound.
Structural formula : It is a formula in which the lines are used between the bonded atoms and the atoms are also shown in the structural formula.
In the structural formula, the lines are used between the atoms.
As per given information of compound we conclude that, there are 4 carbon atoms, 9 hydrogen atoms and 2 oxygen atoms.
Thus, the chemical formula for the given molecule will be, 
That they travel in a vacuum. All other waves require a medium in which they wave.