Due in will mark as brainliest if answered

1. design an experiment that determines the amount of time needed for a person's heart rate to return to an at-rest after exercise.


2. some large veins have one-way valves, which keep blood flowing in one direction. why don't arteries need similar valves?
valves move blood away from the heart, so they can typically move with the force of gravity and there is no need for valves to keep the blood flowing in one direction. but veins carry blood back to the heart, against the flow of gravity. so they are in more need of valves to make sure everything is flowing the same way.