The starting amount of radioactive iodine-131 was 250 g. the half-life is 8 days. when leslie measured the amount, she
measured 15.625 g of radioactive iodine. how many days have elapsed between measurements?

Rain is pulled by gravity which is a non contact force

The objects are acted upon by only one force. gravity. mass times the acceleration of gravity (-9.81meters/second squared).

The answer is water molecules are split.cellular respiration and photosynthesis are complement  reactions to each other. these are reverse reactions. in cellular respiration glucose and oxygen yield water and carbon dioxide. so, when respiration begins,  glucose molecules are split. in the opposite reaction - in photosynthesis, carbon dioxide and water yield glucose and oxygen. thus,  when respiration begins, water molecules are split.