Explorations of Pressure and Variations of Pressure First, what is pressure?  Can you think of examples of pressure?

How is pressure measured? What units are used to describe pressure? Tire pressure is measured how?  What does psi mean? Pounds / Square Inches Pounds: a unit of force exerted Square Inches: on a surface What does “per” mean here?

Co-Variation Questions (Finger Tool) As the area changes, how does the pressure change, assuming the force stays constant. As the force changes, how does pressure change, assuming the area is held constant?

Co-Variation Question (Finger Tool) Why do your ears hurt when you go to the bottom of a pool? As the depth under water changes, how does the pressure change?

What is Force? In SI units: Newton (N)  1 N = the force required to give a mass of 1 kilogram an acceleration of 1 meter per second per second.  9.8 N = the force exerted at the surface of the earth by a 1 Kg mass In English units: Pound (lb)  Often confusing because a pound can be used both as a unit of mass and a unit of force.  What is it in psi?  1 pound-force = the force exerted at the surface of the earth by a 1 pound mass = the force exerted at the surface of the moon by a 6 pound mass

What is Pressure? The pascal [pa] is the SI unit of pressure. 1 pa = the pressure generated by a force of 1 Newton acting on an area of 1 square meter. It is a rather small unit as defined and is more often used as a kilopascal [kPa]. Inches of mercury (inHg) or millimeters of mercury (mmHg or Torr): pressure exerted by a column of mercury 1 inch high (or 1 mm high) bar (bar): 1 bar = 10 5 Pa atmosphere (atm): air pressure at sea level  1 atm = kPa = hPa = mbar  1 atm = 760 mmHg  1 atm = inHg  1 atm = psi

Pressure-Depth Analysis As the depth under water changes, how does the pressure change? Whiteboard as many representations as possible. Start the calculator program to read the pressure sensor: Plug the calculator and sensor into the CBL Press [APPS] Press ▼ (several times to scroll down to “Datamate”) Press Enter

Pressure-Depth Discussion From “Changes” to “Rate of Change” How is this rate represented in the graph? How is this rate represented in the equation? Sliders in Fathom. Use two sliders and a function plot to determine a good value for the rate of change of pressure vs. depth.

Summary Meaning of Pressure Meaning of linear relationship  Repeated addition by constant change in pressure  Proportional amounts of change  Constant rate of change Multiple Representations  Amounts of change  Rate of change