Science mysteries: why do people yawn?
science has given humans many amazing devices and useful bits of knowledge. we know so much about our bodies and how to stay healthy, for example. we also know how to make machines and devices that make life easy for us. scientists dedicate their lives to knowledge, but even with a lifetime commitment, sometimes scientists fail to find all the answers. one mystery that still remains unsolved is why we yawn-what makes us yawn and what purpose it serves.
recent studies suggest that we yawn when we get tired as a way to encourage our brains. the theory is that yawning cool the brain, allowing it to work more efficiently. according to webmd's article about these studies, when you yawn, your jaw muscles get stretched, increasing blood flow to your neck, face, and head. also a deep breath during the yawn forces spinal fluid and blood down from the brain. the cool air then cools down these fluids.
other scientists believe, however, that yawning is a form of communication. this theory attempts to explain why yawning seems to spread from person to person. this kind of behavior is called "contagious yawning" and carries with it a possible social message. scientists are not yet sure what exactly the message is, but they believe people who have more social empathy are more likely to start yawning when they see someone else yawning.
scientists will continue to investigate the mystery of the yawn. is it a leftover behavior from before humans had language? was it a "hey, i'm sleepy. let's go to sleep" message? or is it really just a way to keep our brains cool? while this behavior still is largely a mystery, one thing is certain: you are probably fighting the urge to yawn right about now.
which word from the first paragraph presents the author's view of scientists? (5 points)

believe

dedicate

yawn

fight

1. read the following excerpt from franklin d. roosevelt's "fireside chat 19":

on the other side of the picture, we must learn also to know that guerilla warfare against the germans in, let us say serbia or norway, us; that a successful russian offensive against the germans us; and that british successes on land or sea in any part of the world strengthen our hands.

remember always that germany and italy, regardless of any formal declaration of war, consider themselves at war with the united states at this moment just as much as they consider themselves at war with britain or russia. and germany puts all the other republics of the americas into the same category of enemies. the people of our sister republics of this hemisphere can be honored by that fact.  

the true goal we seek is far above and beyond the ugly field of battle. when we resort to force, as now we must, we are determined that this force shall be directed toward ultimate good as well as against immediate evil. we americans are not destroyers — we are builders.

analyze the effectiveness of this excerpt. how does it function within the speech as a whole? how does the structure of the excerpt to convey the speech's purpose and key points? support your argument with evidence from the speech. (10 points)

this is the answer , p = 1 + (1/10)x

step-by-step explanation:

we have,

at sea level pressure is 1 atmosphere (i.e at x =0, p0=1 atmosphere)

at depth 23 meters , pressure = 3.3 atmosphere

since the pressure increases at constant rate as the depth increases, so we can write a relation as:

p =p0 +   kx   , where p is the pressure  , p0 is the initial pressure, x is the depth and k is constant rate of increasing.

to find constant rate k, plug p = 3.3 , p0 = 1 and x= 23 meters

we get,

  3.3 = 1 + k * 23

k = 2.3 / 23   = 1/10

so we can write the function formula as:   p = 1 + (1/10)x