Lecture 1. Fluids at rest. Physics 103 Spring 2012 Torricelli.

Transcription

1 Lecture 1 Fluids at rest Pascal Physics 103 Spring 2012 Torricelli Andrei Sirenko, NJIT 1 PRESSURE 2012 Andrei Sirenko, NJIT 2

2 DENSITY and PRESSURE in FLUIDS Compressibility Of liquids is very low 2012 Andrei Sirenko, NJIT 3 Crystals What do you know about crystals? They make nice chandeliers!?.. Superman Returns 2012 Andrei Sirenko, NJIT 4

3 2012 Andrei Sirenko, NJIT 5 PRESSURE MEASUREMENT 2012 Andrei Sirenko, NJIT 6

4 PRESSURE MEASUREMENT Magdeburg hemispheres h 2012 Andrei Sirenko, NJIT 7 the pressure increases with depth below the air water interface 2012 Andrei Sirenko, NJIT 8

5 QZ: The figure shows four containers of olive oil. Rank them according to the pressure at depth h, greatest t first Andrei Sirenko, NJIT 9 Measuring Pressure Hg 2012 Andrei Sirenko, NJIT 10

6 Pascal's Principle With a hydraulic lever, a given force applied over a given distance can be transformed to a greater force applied over a smaller distance 2012 Andrei Sirenko, NJIT 11 Hydraulic Breaks With a hydraulic lever, a given force applied over a given distance can be transformed to a greater force applied over a smaller distance 2012 Andrei Sirenko, NJIT 12

7 FLUIDS at REST 2012 Andrei Sirenko, NJIT 13 Buoyant force net upward force is a buoyant force When a body is fully or partially submerged in a fluid, a buoyant force F b from the surrounding fluid acts on the body. The force is directed upward and has a magnitude equal to the weight m f g of the fluid that has been displaced by the body 2012 Andrei Sirenko, NJIT 14

8 Buoyant force When a body is fully or partially submerged in a fluid, a buoyant force F b from the surrounding fluid acts on the body. The force is directed d upward and has a magnitude equal to the weight m f g of the fluid that has been displaced by the body 2012 Andrei Sirenko, NJIT 15 EUREKA! π = Archimedes (287 BC BC) 2012 Andrei Sirenko, NJIT 16

9 Hiero: Is it really 100% gold? (V crown ρ w )g (V gold ρ w )g 1. raft mg mg 2012 Andrei Sirenko, NJIT 17 edu/ crorres/archimedes/claw/illustrations html 2012 Andrei Sirenko, NJIT 18

10 edu/ crorres/archimedes/claw/illustrations html 2012 Andrei Sirenko, NJIT 19 edu/ crorres/archimedes/claw/illustrations html 2012 Andrei Sirenko, NJIT 20

11 Pascal's Principle With a hydraulic lever, a given force applied over a given distance can be transformed to a greater force applied over a smaller distance 2012 Andrei Sirenko, NJIT 21 Archimedes (287 BC BC) Give me a lever long enough and a place to stand, and I will move the world Is it really ypossible??? 2012 Andrei Sirenko, NJIT 22

12 Is it really possible??? F Arch L Arch F Earth F Earth = N F Arch = 600 N (M Earth = kg ) (60 kg) 2012 Andrei Sirenko, NJIT 23 Is it really possible??? D Arch =10 21 m D Earth = m L Arch F Arch F Earth F Arch = 600 N (60 kg) F Earth = N (M Earth = kg ) L Arch /L Earth = ; D Arch /D Earth = D Arch =10 21 m With the power of P=600N m/s, t = s years (people do not live that long) If Archimedes moves his arm with the speed of light, then D Arch =50m during years (life time of the Earth) 2012 Andrei Sirenko, NJIT 24

13 Perpetual Motion and Free Energy 2012 Andrei Sirenko, NJIT 25 Perpetuum Mobile Machine, which works itself forever English: Perpetual Motion 2012 Andrei Sirenko, NJIT 26

14 More Examples: Water Put an innertube on a wheel. Fill it two thirds with wather. Put an axle through it so it can spin. Now make another one like it. Now hold the axels and push the wheel up against each other so that t they can squeez each others wather to the outside. The results are that t one side of each wheel is lighter than its other side. That is why the wheel spins Andrei Sirenko, NJIT 27 More Examples: Water buoyant force of Archimedes' principle: "A body immersed in liquid experiences and upward buoyant force equal to the weight of the displaced liquid." 2012 Andrei Sirenko, NJIT 28

15 Lecture 1 Fluids at rest y Physics 103 Spring Andrei Sirenko, NJIT 29