2.  What is “pressure”, what is “density”, and how do we measure them?  Who contributed to our current ideas and theories about pressure?  Where can we see pressure measured on a daily basis?

3.  In its simplest form, pressure is a force applied over a specific area.  Remember: ◦ Force is a push or pull (measured in Newtons)  Therefore, the equation for pressure is: ◦ Pressure = Force / Area

4.  English Units ◦ psi (pounds per square inch) ◦ psf (pounds per square foot)  Metric (S.I.) Units  Pascal (pa)  Atmosphere (atm)  Bar (bar)

5.  Like most measurements in physics, they are named after the scientist who “discovered” it.  Blaise Pascal was a French scientist and Mathematician from the 1600’s. His work included a hydraulic press and mechanical calculator. He named the units for pressure after himself while working with the hydraulic press. His mechanical calculator is also named after himself, the Pascaline.

6.  Where do we see pressure regularly? ◦ Some examples include:  Tire pressure (measured in psi)  Pistons in a car engine  Blood pressure  Supersoaker Water Gun

7.  Density is defined as “mass per unit volume”  Designated by the Greek letter “rho”: ρ  More dense objects will sink, while less dense objects will float (both in air and in liquid)  This explains why helium floats in air, because helium is less dense.  This also explains why lead sinkers sink in water, because they are more dense than the water.

8. Which do you think is more dense: the yellow liquid or the red liquid? Why?

9.  The equation for density is: ◦ ρ = mass/volume ◦ The units for ρ are [units for mass]/[units for volume]  Examples include:  Kg/m^3  g/mL  Kg/mL

10.  Slide 6 Stethoscope: blog.timesunion.com  Slide 6 Tire Pressure: gadgetrivia.com  Slide 6 Pistons: dichotomistic.com  Slide 6 Super Soaker: shoponline2011.com  Slide 8: apartmenttherapy.com