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Physics 11 Scale UpFall 2014Chapter 13Procedural NotesCh. 13 quiz todayQuiz on Ch. 14 & 15 Friday 21stLab on Balistic Pendulum on Nov. 19th

13 Fluids

3Chapter 13By the end of Ch. 13 you are expected to know how to:draw a FBD for bodies immersed in fluids,calculate and compare buoyant forces and hydrostatic pressures,apply Pascals Principle, the Archimedes Principle, the equation of continuity and the Bernoullis equation to find different physics quantities (mass, density, volume, velocity, cross sectional area)Chapter 13

PressureThe pressure of the water behind each hole pushes the water out.

The SI unit of pressure is 1 pascal = 1 Pa = 1 N/m2.

Pressure in a Liquid Increases with Depth

Buoyant force is due to different pressures at the top and bottom of a submerged object.

This leads to:upward net force

Bernoullis equation :

high speed (fast) low pressurelow speed (slow) high pressureContinuity equation :A1v1 = A2v2 = constant

wide (BIG area) low speednarrow (small area) high speedSummary of Fluid Motion

constant

If the fan blows the air between the Elmo balloons at 3m/s, what is the force acting to push the balloons together? Kissing Elmos

If the density of Helium in the balloon is 0.1664 kg/m3 and the density of air is 1.205 kg/m3, and the empty balloon weighs ? what extra weight must be tied to the balloon to stop Elmo from blowing away? Kissing Elmos

A sphere completely submerged in water is tethered to the bottom of a pool by a string. The tension in the string is 1/3 the weight of the sphere.

What is the density of the sphere?13.49r = 750 kg/m3A light liquid with r1 floats on top of a denser liquid with r2. A uniform cylinder of length L and intermediate density r (r1 < r < r2) floats at the interface as shown.

15.52

12hWhat fraction of the cylinders length is in the denser liquid?

A pipe flowing with oil has two pressures gauges on it. The reading on the lower pressure gauge is shown. What does the top pressure gauge read?

roil = 900 kg/m313.33P = 110 kPaChapter 13By the end of Ch. 13 you are expected to know how to:draw a FBD for bodies immersed in fluids,calculate the buoyant force,use Pascals Principle and the Archimedes Principle in equation form,use the equation of continuity and the Bernoullis equation,manipulate them to find different physical quantities.Chapter 13

Homework QuestionsA glass of water is filled to the very top with water and four ice cubes. When all of the ice cubes melt, what happens to the water level in the glass?

Buoyant ForcesThe water level rises, so some water spills out.The water level goes down.The water level stays the same, right at the top.

Buoyancyupper bricklower brickboth the sameYou are asked to hold one of these two bricks in the indicated position. Which of the two bricks will be easier for you to hold?

20BuoyancyB > C > A(A = B) > C C > A > BC > (A = B)A = B = CRank the weights of the beakers, including their contents, from largest to smallest.

21The Falkirk Wheel

22The Falkirk Wheel

23Buoyancyship Aship Bboth the same

Ships A and B have the same height and the same mass, but they have different cross-sectional profiles. Which ship rides higher in the water (i.e. more height above water line)?AB

24Buoyancyfloats as beforefloats higher in the waterfloats lower in the watersinks to the bottomAn object floats in water with 3/4 of its volume submerged. The object is now placed in oil with a density half that of water. What happens?

25Buoyancymove up slightlystay at the same placemove down slightlysink to the bottomfloat to the top

up to surfaceAn object floats in water with 3/4 of its volume submerged. More water is now poured on top of the water, totally covering the object. When the object is released it will:

26Buoyancymove up slightlystay at the same placemove down slightlysink to the bottomfloat to the topAn object floats in water with 3/4 of its volume submerged. Oil is now poured on top of the water, totally covering the object. When the object is released it will:up slightly

27Liquid flows through this pipe. What you are seeing is an overhead view of the pipe.

Rank the flow speeds at points 1-4 from largest to smallest.15.21Rank the pressures at points 1-4 from largest to smallest.V1>(V2=V3)>V4P4>(P2=P3)>P1