Workbook Chapter 9: Facts about Liquids is about:
Density: r = Mass/Volume density of water rw = 62.4 lb/ft3 = 1000 kg / m3 = 1g/ml = 1g/cm3
Pressure: P = Force/Area P atm = 1 atm = 14.7 lb/in2 = 1.013 x 105 N/m2 = 1 Pascal = 1Pa
Pascal's Law: Pressure applied to a liquid is transmitted equally throughout.
Archimedes Principle: Objects immersed in liquids are bouyed up by a force equal to the weight of the fluid displaced.
Torricelli's Law: Velocity of fluid from hole a depth h below the surface has same velocity as object dropped from height h.
Continuity Law: A1 V1 = A2 V2 , leads to
Bernoulli's Equation : P + .5rv2 + rgy = constant
Assumption: Liqiuds are incompressible

Pressure P=Force/Area

Pressure is created by molecules banging into each other billions of times per second.
The average speed of a water molecule in a glass of water is 1000 m/s !

Pressure is nondirectional. (Force is the same in all directions)

Pressure P is a function of depth only in liquids or solids. (independent of shape of container.)




Pascal's Law : Pressure applied to a confined liquid is transmitted eqully throughout the liquid.

 

Example: If F1 = 20 lb and cylinder 1 was 1 inch in diameter, and cylinder 2 was 1 foot in diameter, would F2 be able to lift a 2000 lb car ?
 

Archimedes Principle: FB = mfluid displaced g


Torricelli's Law: v = ˆ2gh




C ontinuity Law: A1 v1 = A2 v2



Bernoulli's Principle: When fluids flow, (or gasses) where pressure is high, velocity will be low, and where pressure is low, velocity will be high. makes birds and airplanes fly. PB 1201-Q1

BONUS QUESTION: In the diagram below, the cross-sectional area of the left-hand piston is 1 m and that of the right-hand piston 16 m2. What size load on the right-hand piston will keep the fluid levels the same?

1. 16kg

2. 1.6kg

3. 160 kg

4. insufficient information PC 1201-Q1

QUESTION 1: Can a battleship float in a bathtub? (imagine a very big bathtub and/or a small battleship; see figure) Suppose the ship weighs 100 tons and the water in the tub weighs 100 kg. There is just a little bit of water all around and under the ship. Will it float or touch the bottom?








1 . it will float if there is enough water to go all around it,

2. It will touch the bottom because the ship's weight exceeds the water's weight

PC 1201-q2



QUESTION 2: Which weighs more?




1. A bathtub brim full of water,


2. A bathtub brim full of water with a battleship floating in it,


3. Both weigh the same amount.
PC 1201-Q3


QUESTION 3: A block of balsa wood with a rock tied to it floats in water. When the rock is on top as shown, exactly half the block is below the water line. When the block is turned over so that the rock is underneath and submerged, the amount of block below the water line is


1. less than half

2. half

3. more than half PC1201-Q4

QUESTION 4: Consider the balsa wood/rock system once again.


Again, the block is turned over so that the rock is underneath and submerged. When the block is overturned, the water level at the side of the container will

1. rise

2. fall

3. remain unchanged PC 1201-Q5



QUESTION 5: The Sierra Light and Power Company has a dam fifty feet high with a tiny lake behind it. Not far away the Department of Reclamation also has a damÐonly forty feet high, but with a hugh lake behind it. Which dam must be strongest?

1. The Sierra Light and Power dam must be strongest

2. The Department of Reclamation dam must be strongest

3. Both must have the same strength

PC 1201-Q6

QUESTION 6: How do the forces Fl, F2, and F3 on the equal areas at the base of the columns compare?


l.F2 > FI > F3


2. Fl = F2 = F3


3. not enough information PB 1203-Q1


BONUS QUESTION: Ten liters of water per minute is flowing through this pipe. Which is correct: The water goes





1. fastest in the wide part of the pipe


2. fastest in the narrow part of the pipe


3. at the same speed in both the wide and narrow parts PC 1203-Q1


QUESTION 1: This was a favorite question of the noted hydrologist, George J. Pissing, and is still often asked of graduate students during oral exams. Consider a bucket of water with two holes through which water is discharged. Water can be discharged through a hole B at the bottom the bucket a distance d below the water surface, or it can be discharged through a downspout which starts at the top T and has its opening at the same distance d below the water surface. Neglecting any friction effects, compared with the water coming out of the downspout, the water coming out of hole B has

1. more speed
2. less speed
3. the same speed PC 1203-Q2

QUESTION 2: Two fat pipes are attached directly to the bottom of a water tank. Both are bent up to make fountains, but one is pinched off to make a nozzle, while the other is left wide open. Water squirts

1. above the water level of the tank from the pinched pipe, below it for the wide open one

 

2. equal to the water level of the tank from both pipes

 

3. less than the water level of the tank from both pipes, but equal for both pipes

 

4. less than the water level of the tank from both pipes, but higher from the pinched pipe than the wide open one PC 1203-Q3


QUESTION 3: In front of a restaurant coffee maker is a glass tube called a sight pipe. The level E of the coffee in the sight pipe is equal to the level of the coffee inside the machine. When the faucet is opened and a current of coffee runs out of the spigot, the level of coffee in the sight pipe






1. suddenly drops to D

2. remains essentially at E

3. surges up to U