A controlled experiment is when scientests go throw thests to make an experiment
Answer:
The polarity of water molecules means that molecules of water will stick to each other like when unlike charges attracts. This is called hydrogen bonding.
Polarity makes water a good solvent, gives it the ability to stick to itself (cohesion), stick to other substances (adhesion), and have surface tension (due to hydrogen bonding).
When the two hydrogen atoms bond with the oxygen, they attach to the top of the molecule. This molecular structure gives the water molecule polarity, or a lopsided electrical charge that attracts other atoms. The end of the molecule with the two hydrogen atoms is positively charged.
Explanation:
The position of the first ball is
while the position of the second ball, thrown with initial velocity 
, is
The time it takes for the first ball to reach the halfway point satisfies
We want the second ball to reach the same height at the same time, so that
