fluids

Question 1

define the states of matter

Answer 1

solid - definite shape and volume
liquid - takes shape of container, but has definite volume
gas - takes shame and volume of contianer

special states:
plasma
bose-einstein condensate

Question 2

define density

Answer 2

represented by Greek letter “rho”
rho = p
kilograms per cubic meer

Question 3

define FLUID

Answer 3

material takes that shape of its container and yields easily to external pressures (gases and liquids are fluid)

Question 4

are liquids compressible

Answer 4

generally no, that’s why hydraulics work, and generally the work is defined as…

Question 5

pressure

Answer 5

P = Force/area

N / m^2

N / m^2 is known as a pascal

Question 6

how does pressure change as we go deeper in a fluid

Answer 6

increases LINEARLY, P = P0 + pgh (small p intentional)

Question 7

guage pressure

Answer 7

delta P = pgh, change does not take into account that initial P0 bcz its change

Question 8

what is change in pressure also known as?

Answer 8

gauge pressure, difference in initial and absolute pressure, a measuring device will probably tell you the gauge pressure, not absolute pressure

Question 9

when an object is submerged in water, pressure is (greater/less than/equal to) at the top of the object and (greater/less than/equal to) at the botton of the object

Answer 9

less at the top, greater at the bottom, as the deeper you go the higher the pressure

Question 10

what is the pressure of an object in a fluid when the fluid is at rest?

Answer 10

hydrostatic pressure

Question 11

pressure depends on (depth, total amount of water in container, shape of container)

Answer 11

assuming the atmospheric pressure is the same, depth only! (even if the surface is not directly aligned with the point of pressure, such as a winding cave going very far to the left)

Question 12

absolute pressure

Answer 12

P = P0 + pgh (where small p = density)

Question 13

define pascal’s law

Answer 13

pressure applied to a fluid, when the fluid is contained everywhere else, is applied by that same fluid in every other direction with equal force over equal areas

Question 14

given a cube with a 1 inch^2 opening, with 10 lbs of force applied to a stopper within the opening, what is the total resulting force acting on the bottom of the container? (the bottom has an area of 20 in^2)

Answer 14

200 lbs

Question 15

in a closed system, the (pressure/force) is the same everywhere

Answer 15

PRESSURE, the FORCE depends on the surface areas of different parts of the system

Question 16

archimedes’ principle

Answer 16

the buoyant force of an object is equal to the WEIGHT (force of the MASS, N O T volume) of the fluid displaced
Fb = pVg

Question 17

define buoyancy

Answer 17

the upward force of an object within a fluid/net force from fluids surrounding an object

Question 18

(true/false) buoyant force is dependent on object depth

Answer 18

false, as we are assuming that ideal fluids are incompressible and thus density does not change

Question 19

why is the pressure the same at the same height despite different amounts of water?

Answer 19

greater total force at that z depth plane, yes, but more spread out

Question 20

in what direction does pressure act?

Answer 20

all directions, with all normal forces perpendicular to the walls

Question 21

RMR: CONSERVATION OF FORCE IS NOT A THING

Answer 21

that’s why pascals law works!

Question 22

pressure equation

Answer 22

P = Force/area

Question 23

what is conserved in a hydraulic system?

Answer 23

work!

work = force * distance,
as you increase force due to pressure it moves less distance up on the heavier side

Question 24

archimedes’ principle

Answer 24

object is buoyed up by force = to the WEIGHT of the fluid displaced

weight of fluid with same volume

Question 25

buoyant force takes into account the….

Answer 25

FLUID, Fb = density * volume * gravity

density and volume are OF THE FLUIDDDDDDDDDDDDDDDd

Question 26

an iceberg with an average density of 910 kg/m^3 and a mass of 52,000 kg floats in sea water with a density of 1030 kg/m^3
a. What is the buoyant force acting on the iceberg?
b. What percentage of the iceberg is submerged beneath the water?

Answer 26

a. its FLOATING! thus net force is zero, thus
52,000 * gravity = 510,120 N = FB

b. solve for TOTAL volume, 52,000/910, = 57.1 m^3

Buoyant force = the weight of water displaced —-> we can find the water displaced!

510,120 N = pv * g

510,120 /(9.81 * 1030) = v

v = 50.5 m^3 of water displaced, thus 50.5 m^3 of iceberg covered!

50.5/57.1 * 100 = 88.44%!!!!!

Question 27

continuity equation (fluid moving through a pipe)

Answer 27

A1v1 = A2v2

same amount of fluid, given a larger area input a smaller area output must have a larger velocity of output

1 kg/second = 1 kg/second, CONSERVATION OF MASS IN A FLOW

Question 28

mass flow rate

Answer 28

in a fluid with an area of high pressure and an area of low pressure, the high pressure will flow into the low pressure area

this is doing force, kind of like a transfer of energy

thus along came bernoulli

Question 29

Bernoulli’s principle

Answer 29

higher velocity =lower pressure in a fluid flow

Question 30

how does a spinning ball curve?

Answer 30

ball is spinning, on one side spinning with the air, thus speed of air relative to surface of ball is different on front and back side, thus motion

Question 31

how does a ball float on a leafblower’s stream of air even when moved from side to side?

Answer 31

because the leaf blower creates a low pressure system by increasing speed, thus the surrounding air has higher pressure and keeps it in the “column”

Question 32

describe the same fluid moving through different sized areas via the continuity equation

Answer 32

LARGER area = slower, lower pressure

SMALLER area = faster, higher pressure

Question 33

Bernoulli’s equation

Answer 33

pressure + 1/2 * density * velocity^2 + density * gravity * initial height = pressure(2) + 1/2 * density * velocity^2 + density * gravity * height

P1 + 1/2pv0^2 + pgy = P2 + 1/2pv^2 + pgy

basically conservation of energy, at one location given the same flow it will be the same at another location

(effectively adding pressure, “kinetic energy,” and “potential energy”)

Question 34

water circulates thru a house in a hot-water heating system. if the water ris pumped at a speed of 0.5 m/s through a 8.0 cm diameter pipe in the basement under a pressure epf 3.0 atmp, what will be the flow speed and pressure in a 5.2 cm diameter pipe on the second floor 5.0 meters above?

Answer 34

2.5 x 10^5

bernoulli’s equation + continuity equation

pressure decrease makes sense conceptually because the area is smaller so it goes faster, as well as the height beneath the water decreasing thus the pressure also decreases

Answer 35

we know that at the opening pressure is atmospheric pressure because, well, its an opening, so P2 = 1.0 x 10^5, and we can use bernoulli’s equation to set it up because its still technically part of the system

we can use Bernoulli’s equation to set up this:

200000 + 1.210002^2 + 0 = 100000 + 1/21000v^2 + 1000*9.8 * 0.7

v = 13.8 m/s

plug it into the conservation of energy or kinematic equation:

1/2mv^2 = mgh
1/2(13.8)^2 = (9.81)h
h = 9.7 meters!!!

Question 36

large soda bottle with a hole in the side

Answer 36

when area of fluid at the beginning area is substantially larger to make its velocity neglible compared to the tiny output:
gh = 1/2v^2