1. 0 10080604020 Average Scores* (over 1 st 2 Exams) * doesn’t include homework score

2. This next week we’ll finish up fluids with the study of fluid flow Friday Fluid moving through things and things moving through fluids. Monday Objects traveling through the airstream. Wednesday Lift and flight.

3. Then jump to Chapter 10 so we can cover electricity, electronics, and light!

4. Beading is evidence that water sticks to itself.

5. Droplets run slowing down surfaces & pull slowly away from surfaces as they fall. evidence that water sticks to materials.

10. We describe this stickiness of a fluid (even water and air exhibit it) by the term “viscosity”. FLUIDVISCOSITY ( ) Air (20 o C) 0.0000183 Water (20 o C) 0.00100 Olive oil (20 o C) 0.0840 Honey (20 o C) 1000

11. fast flow Consider flow through a section of garden hose of diameter, D slow flow stationary/crawling D

12. Without viscosity, flow rate would be simple: In a time interval of 1 second (  t = 1 sec) all water in the pipe would flow how far? A. v /  t B. v  t C. v  t 2 Flow rate: gallons/minute liters/minute cc/sec m 3 /sec volume per unit of time At a constant flow rate,each and every second a fixed volume of water would flow past any given point. v 1212

13. Without viscosity, flow rate would be simple: In a time interval of 1 second (  t = 1 sec) what volume of water passes through A? A. v   tB. A  v  t C. A  tD. A  v v 1212 vtvt So the flow rate would be Volume second = AvtAvt tt = Av How does the flow rate depend on the hose or pipe’s diameter? A. rate  DB. rate  D 2 C. rate  1/D D. The rate does not depend on D

14. Volume second  D2D2 So simple geometry argues the flow rate depends at least on The other factor ( other than cross section ) was v. What effects the speed of the fluid through a section of hose? P1P1 P2P2 As the differential pressure  P = P 1 – P 2 increases, the flowrate can be expected to A. increase B. stay the same. C. decrease.

15. Volume second  PD2PD2 So far we expect: Viscous forces provide a friction which can keep fluids from accelerating continuously. The greater a fluid’s viscosity, , A. the greater the flowrate. B. the smaller the flowrate. C. has no effect on the flowrate. Which relationship below best seems to represent this dependence on viscosity? A.B. C.D.

16. Volume second  PD2PD2 So far we expect: Viscous forces act everywhere the fluid needs to slide past the inner hose wall. The greater a length, L, of hose A. the greater the flowrate through it. B. the smaller the flowrate through it. C. has no effect on the flowrate. Which relationship below best seems to represent this dependence on viscosity? A.B. C.D. 

17. fast flow slow flow D We’ve noted that fluid far from the inner walls of the hose travels the most freely. In fact like blood in a capillary tube or mercury in a thermometer even water will not dribble freely from a narrow enough straw.

18. fast flow slow flow D This makes the dependence on D even stronger than the simple geometry of the size of the opening. Volume second  PD2PD2 LL 4

19. Volume second  PD4PD4 LL Over the years mineral deposits have narrowed (mainly) the hot water pipes throughout your folk’s home. The hot water pipes must have an effective inner diameter now ___ times the size of the cold water pipes. A. B. C.D. E.F. City water pressure hasn’t really changed, but the hot water’s flowrate is about half that of the cold water. 4

20. Volume second  PD4PD4 LL You’re watering the backyard, but can’t reach the very back corners. You attach a 2 nd identical hose to increase your reach. The flow rate A. doubles. B. remains unchanged. C. is halved. D. is about ¼ what it was.

22. At the bend in a pipe, along the outside curve, the pressure A. decreases. B. can’t change. C. increases. At the bend in a pipe, along the outside curve, the water’s speed A. decreases. B. can’t change. C. increases.

23. Water slows down and backs up against the outside wall. The streamline broadens to show this.

24. At the bend in a pipe, along the inside curve, the pressure A. decreases. B. can’t change. C. increases. Viscosity may make the fluid “cling” to the inside wall of the pipe and try to follow the curve… At the bend in a pipe, along the inside curve, the water’s speed A. decreases. B. can’t change. C. increases.

25. Water slows down and backs up against the outside wall. The streamline broadens to show this. Water speeds up and races ahead along the inside wall. Streamlines thin to show this! Stream- lines regain their more even distri- bution along straight sections of pipe.

26. Water slows down and backs up against the outside wall. Water speeds up and races ahead along the inside wall. Constant “energy/volume” Bernoulli’s principle argues that the fluid pressure must be A. greater along the inside of the curve. B. greater along the outside of the curve. C. exactly the same along inside and outside.

27. Inside curve Outside curve The pressure gradient points (from region of highest pressure toward region of lowest pressure) A. to the right.B. to the left. C. into the screen (away from you). D. toward the center of curvature.

28. Inside curve Outside curve Notice the pressure gradient forces fluid toward the center of its curved path…providing the centripetal force that ANY mass needs to turn a corner!