Pressure Section 6.1

What is pressure? It’s related to the word press Go ahead… press your finger on your hand press harder press lighter You are changing the amount of force Pressure refers to a force pushing on a surface

Calculating Pressure Pressure = Force / Area Area of a rectangle = base x width Pressure is measured in Pascals Force is measured in Newtons Area is measured in m2 or cm2 The larger the area of contact, the smaller the pressure The smaller the area of contact, the larger the pressure

Try it! If you poke your hand with your opposite thumb with 12N of force. Your thumb is roughly 1 cm by 1 cm. Calculate the pressure that you are exerting. Now, press your thumb nail into your hand with the same force as before. Which hurt more, your thumb or your thumb nail? Explain why!

Try It! Create a solve for A Create a solver for F

Fluid Pressure Fluid – a substance that can easily flow can change shape. Solids cannot be fluids. Liquids and gases can. In fluids, molecules are constantly moving in all directions All of the forces exerted by the individual molecules in a fluid add together to make up the pressure exerted by the fluid.

Why does the atmosphere exert pressure on you? The atmosphere is gas Gas is a fluid Fluids exert pressure So, the atmosphere exerts a pressure on you

Balanced Pressure If the atmosphere is exerting pressure on me, why don’t I feel it like I did when I pressed on my palm with my thumb??? In a fluid that is not moving, pressure at a given point if exerting equally in all directions. Air is pushing on the palm of your hand at 10.13 N/cm2 it is also pushing on the back of your hand at 10.13 N/cm2 Pressure inside of your body balances pressure outside of your body

Variation in Fluid Pressure Have your ears ever popped in a plane? Air pressure decreases as elevation increases The higher you go, the less the pressure Have you ever dove too deep and your ears hurt? Water pressure decreases as depth increases The deeper you go, the higher the pressure