1 / 14

PHYSICS 231 Lecture 22: Pressure

PHYSICS 231 Lecture 22: Pressure. Remco Zegers Walk-in hour: Thursday 11:30-13:30 am Helproom. Previously. Young’s modulus. Solids:. Shear modulus. Bulk modulus Also fluids. General:. P=F/A (N/m 2 =Pa) =M/V (kg/m 3 ). Force and pressure. Air (P=1.0E+5 Pa). P=0 Vacuum. A. F.

dean
Download Presentation

PHYSICS 231 Lecture 22: Pressure

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. PHYSICS 231Lecture 22: Pressure Remco Zegers Walk-in hour: Thursday 11:30-13:30 am Helproom PHY 231

  2. Previously Young’s modulus Solids: Shear modulus Bulk modulus Also fluids General: P=F/A (N/m2=Pa) =M/V (kg/m3) PHY 231

  3. Force and pressure Air (P=1.0E+5 Pa) P=0 Vacuum A F What is the force needed to move the lit? PHY 231

  4. Magdeburg’s hemispheres Otto von Guericke (Mayor of Magdeburg, 17th century) PHY 231

  5. Pressure vs Depth Horizontal direction: P1=F1/A P2=F2/A F1=F2 (no net force) So, P1=P2 Vertical direction: Ftop=PatmA Fbottom=PbottomA-Mg=PbottomA-gAh Since the column of water is not moving: Ftop-Fbottom=0 PatmA=PbottomA-gAh Pbottom=Patm+ gh PHY 231

  6. Pressure and Depth: Pdepth=h =Pdepth=0+ gh Where: Pdepth=h: the pressure at depth h Pdepth=0: the pressure at depth 0 =density of the liquid g=9.81 m/s2 h=depth Pdepth=0=Patmospheric=1.013x105 Pa = 1 atm =760 Torr Pascal’s principle: If P0 changes then the pressures at all depths changes with the same value. PHY 231

  7. A submarine A submarine is built in such a way that it can stand pressures of up to 3x106 Pa (approx 30 times the atmospheric pressure). How deep can it go? PHY 231

  8. Does the shape of the container matter? NO!! PHY 231

  9. Your homemade pressure difference meter (PART I) Pdepth=h =Pdepth=0+ gh h1 Part 2 on Friday! h2 PHY 231

  10. Pascal’s principle In other words then before: a change in pressure applied to a fluid that is enclosed in transmitted to the whole fluid and all the walls of the container that hold the fluid. P=F1/A1=F2/A2 If A2>>A1 then F2>>F1. So, if we apply a small force F1, we can exert a very large Force F2. Hydraulic press demo PHY 231

  11. Hydraulic brake What is the frictional torque about the axle exerted by the shoe on the wheel drum when a force of 44N is applied to the pedal? F=44N 6.4cm2 1.8 cm2 R=0.34 m coef of friction: 0.5 PHY 231

  12. Pressure measurement. The open-tube manometer. The pressure at A and B is the same: P=P0+gh so h=(P-P0)/(g) PHY 231

  13. Pressure Measurement: the mercury barometer P0= mercurygh mercury=13.6E+03 kg/m3 mercury,specific=13.6 PHY 231

  14. Pressure at different altitudes The pressure in the lecture room equals 1 atm (1.013E+05 Pa). What will the pressure on the 6th floor of the BPS building be (h=20m)? And at the top of mount Everest (h=8500 m)? PHY 231

More Related