What is pressure at see level?

What is pressure? 

Wind gust to 150mph. What is pressure differential in tons accrossa flat roof with an area of 300m^2

What is the apparent weight of a sphere that is 10kg in a mass witha radius of 0.1 meters? In newtons

What is pressure in pascals on a diver at a depth of 45meters? Theatmospheric pressure above teh surface of the water is 101kPa. ansin liter/sec

Can you describe what a pressure cooker does? How does the higher pressure in a pressure cooker effect the temperature reached and why? Why is there a limit on the cooking temperature in boiling water (at normal pressure) no matter how much you heat it?