Ciencias Fisicas e Ingenieriles

8/17/2019 Ciencias Fisicas e Ingenieriles

1/107

Physics and Engineering Sciences

(Part 2)


2/107

Units of MeasureChapter 2


3/107

United States Measurement

Systems• International System of Units (SI) – Metric

• U.S. Customary System


4/107

T 2-1

SI Base Units


5/107

T 2-3

Metric Values


6/107

T 2-6

U.S. Customary System


7/107

T 2-7

U.S. Customary System

Conversions


8/107

LightChapter 3


9/107

Electromagnetic Radiation

• Light is electromagnetic radiation

• Light is that portion that is visible to the

human eye


10/107

Light

F 3-1 Electromagnetic Spectrum


11/107

• The product of the wavelength and frequency of light is

equal to its speed:

• C = v

• Where c is the speed of light in a vacuum in m/s, is the

wavelength in m, and v is the frequency in cycles per

second or hz.

F 3-2 Sensitivity of the eye to light


12/107

Ray Theory

• A ray of light is a straight path that the

light travels in from one point to another

• Two basic types:1. Reflection

2. Refraction


13/107

Reflection

F 3-3 Reflected light


14/107

Refraction

F 3-4 Light refracted


15/107

T 3-1

Material

Air 1.00

Water 1.33

Fused Quartz 1.46

Flint Glass 1.66

Diamond 2.42

Various indices of refraction


16/107

1 2

2 1

2

1

2

2

sin

sin

sin 45 1.33

sin 1.00

.707sin

1.33

32

F 3-5 Light refracted


17/107

SoundChapter 4


18/107

Sound

• Sound is the transmission of mechanical

waves in matter

• Sound can only be transmitted through

matter and cannot be transmitted in a

vacuum


19/107

Wave Nature of Sound

• Sound is comprised of longitudinal

mechanical waves traveling through matter

• Sound waves are generated by the

successive compression and rarefaction of

the media that is transmitting it


20/107

Sound

F 4-1 Generation of sound waves


21/107

Intensity of Sound

The intensity of sound P is a measure of the

energy that it transmits. Intensity is defined

as:

I INTENSITY Surface Area

Power

Area

Energy

Time


22/107

Relative Intensity

2

12 2

Relative Intensity (dB) = 10log

where,

actual intensity( / )

10 /

o

o

I

I

I w m

I w m


23/107

Frequency of Sound

• The frequency of sound is normally referred

to as its pitch. Pitch describes the audible

effect that a frequency of sound waves has

on the human ear. Pitch is normally

measured in hertz (Hz) or cycles/second.


24/107

Sound


25/107

pitch rev

s

holes cycles

rev

cycles

s Hz

12001

60

48

960 960

min

min ( )

Ex 4.3.1


26/107

Typical Sound Intensities

Sound Type Intensity

W/m2 dB

Jet Aircraft (close range) 1 120

Jackhammer 10-2 100

Automobile on Highway 10-4 80

Normal Speech 10-6 60

Whisper 10-10 20


27/107

F 4-2 Response of average human ear to sound at different frequencies

Response of The Human Ear to Sound


28/107

Electricity/ElectronicsChapter 5


29/107

Electricity/Electronics

• Electricity and electronics are interrelated

phenomena. They are involved in the

generation, transmission, and storage of

power in numerous applications.


30/107

Electrical Circuits

• Electrical circuits contain a source of

electrical power, passive components which

dissipate or store energy, and activecomponents which change the form of

electrical power.


31/107

Electrical Currents

• Direct current (DC) - current and voltage

does not vary with time

• Alternating current (AC) - current and

voltage varies (usually sinusoidally) with

respect to time


32/107

Electrical Quantities

Charge (Q) Electrical charge is an energy carrying quantity

that is measured in units of coulombs.

Current (I) Electrical current is the time rate of flow of

charge past a point in a circuit and is measured

in Amperes.

Voltage (V) Voltage is the change in energy per unit charge.

The unit of measure is the volt.


33/107

Energy (W) Electrical energy is the capacity to do

work. Energy is measured in joules.

Power (P) Electric power is the time rate of energy

flow. Electrical power is measured in

watts.

Resistance () Resistors are energy absorbing com-

ponents. Resistance is measured in ohms.


34/107

Circuit Components

• Resistors are energy absorbing elements

• Inductors are energy storing components where energy is

stored in a magnetic field

• Capacitors are energy storing components where energy is

stored in an electrical field


35/107

F 5-2 Parallel and series connections

Circuit Connections


36/107

Circuit Rules


37/107

Ohm’s Law

E = IR

I = E/R

R = E/I


38/107

R R R R

R

1 2 3

21 5 4

75

. .

.

1 1 1

1

3

1

721

1 2 R R R

R

.

30+

-

V

Calculate Equivalent Resistance


39/107

30

+

-

V

I

E

R

I

I A

3075

4

.



40/107

R R R

R

1 2

5 19

24

1 1 1

1

24

1

8

6

1 2 R R R

R



41/107

R R R

R

1 2

6 15

21

1 1 1

121

19

63

1 2 R R R

R

.



42/107


R R R R

R

1 2 3

63 2 2

85

. .

.

I E

R

I A

1785

2

.


43/107

F 5-3 Parallel and series connections of various components


44/107

Circuit Analysis Using

Kirchoff’s Laws • Kirchoff’s Loop Rule (KLR) is a statement of

conservation of energy. It states that the sum of

voltage rises or drops around a closed path or loopmust be zero.

• Kirchoff’s Point Rule (KPR) is a statement of

conservation of charge. It states that the flow of

charges (current) into or out of a point (junction of

electrical connections) must add to zero.


45/107


46/107

StaticsChapter 6


47/107

• Analysis of mechanical equilibrium of

rigid bodies subjected to force systems

• Analysis is restricted to bodies at rest

Statics


48/107

Statics

F 6-1 Transmissibility of forces


49/107

F 6-2 Resultant of two forces


50/107

F 6-3 Reaction to an applied force


51/107

F 6-4 Rectangular components of a force


52/107

Given: Three Forces: F1, F2, F3

Find: Resultant and Force

F 6-5 Forces applied to an eyebolt


53/107


54/107

• A moment is the tendency to rotate that a

force imparts to a rigid body

• The magnitude of the moment is the productof the magnitude of force and the perpendicular distance between the line of

action of the force and the point or axis ofrotation

Moment of Force


55/107

F 6-6 Moment of a force about a point

Moment of Force


56/107

• A couple is formed when two forces of

equal magnitude and opposite sense

with parallel lines of action

Force Couples


57/107

F 6-7 A couple resulting from a system of forces

Force Couples

d i


58/107

• Isolate the body from the ground of any bodies in contact with it

• Indicate all external forces acting on a body

• Identify the magnitude and direction ofreactions from the ground or other bodies in

contact by the application of Newton’s FirstLaw

Free-Body Diagram

Procedure


59/107

F 6-8 Simple supported beam and corresponding free-body diagram

Free-Body Diagrams


60/107

• The force of friction acts opposite to thedirection of any impending motion thatwould result from an applied force

• To overcome friction and cause a body tomove, a force F must be applied that isgreater than or equal to force of friction

• F = uN• u = coefficient of friction and N = the

normal force

Friction


61/107


62/107

DynamicsChapter 7


63/107

• Kinematics: the study of the motion of particles

and bodies.

• Kinetics: the study of the forces and moments

required to induce motion.

Dynamics

(Bodies in Motion)


64/107

An automobile skids to a stop in 200 ft. after its brakes are

applied when it was moving at 60 miles per hour. Find the

acceleration in units of ft/s2, assuming the deceleration is

constant.

Solution: The initial velocity must be put in appropriate units.

v mileshour

hour s

ft mile

060 1

36005280

Rectilinear Motion


65/107

The following equation of rectilinear motion will be applied:

v v as2

0

2 2

If the final velocity is taken as zero, this equation can be

algebraically rearranged to yield:

a v

s

ft

s 0

2 2

2

88

2 20019 4 2

( )( ).

The negative sign indicates that the vehicle is decelerating.


66/107

F 7-1 Angular Motion

Angular Motion


67/107

Work is defined as the product of an applied force,

F, and the distance over which the force is applied,s. For a constant force, this relation is given by:

W = F · s

Energy Methods

Ki i E


68/107

For a body in linear motion, this is given by:

KE mv 12

2

For a body in angular motion, this is given by:

KE I 1

2

2

Kinetic Energy


69/107

Strength of Materials

Chapter 8


70/107

Strength of Materials

• Strength of materials is the study of

deformable bodies subject to applied

forces and moments.


71/107

Issues: Strength of Materials

• How much load can be safely applied to a

structure or component?

• What material should be chosen to fabricate acomponent to safely withstand a particular load?

• How much will a component deflect under load?


72/107

Stress/Strain Loading

• Axial Loading: If an object is subjected to a positive strain in one direction, it is normal for the

object to contract or experience a negative strainin another direction.

• Torsional Loading: Shafts and other machineelements that are subjected to equilibrating

couples at each end (torque) are in torsion.


73/107

Stress/Strain Loading

• Beam Loading: Beams are machine elementsthat are typically much longer than they are wide

and are loaded in a direction that is perpendicularto their long dimension.

• Column Loading: A column is a long slendermember that is loaded axially in compression.


74/107

Tension

Compression


75/107

Shear

Rivet Under Shear Stress

LOAD FORCE ON A STEEL BEAM


76/107

LOAD

FORCE

STRAIN

PERMANENT DEFORMATION

ELASTICITY


77/107

Combination of Forces on a

Structural Member


78/107

Torsional Load


79/107

F 8-4 Shaft loaded in torsion

Torsional Loading


80/107

F 8-5 Steel rod in torsion

Torsional Loading


81/107

Thermodynamics and

Heat TransferChapter 9

Thermodynamics


82/107

Thermodynamics

andHeat Transfer

•The thermal properties of matter are

controlled by temperature

•Temperature is a measure of thetendency of an object to absorb or

dissipate energy in the form of heat


83/107

Kº = Cº + 273º

Cº = 5/9 (Fº - 32º)Fº = 9/5 Cº + 32º

Temperature Conversions


84/107

Thermal Expansion

• The dimensions of most solid materials will

expand and contract with increasing and

decreasing temperatures. The change in a lineardimension, such as length or diameter, is

proportional to the change in temperature of the of

the object T, its length L and a constant , the

coefficient of expansion.


85/107

F 9-2 Expansion by increase of temperature

Expansion of an Object

A brass sheet has a 2.000 inch diameter hole at 70F. The sheet is


86/107

F D a D T x F in F

in

FHGG

IKJJ

6

106 10 2000 230

005

. .

.

b ge j

A brass sheet has a 2.000 inch diameter hole at 70 F. The sheet is

heated to 300F. Find the new diameter of the hole.

The change in diameter can be found as:

**Therefore, the new diameter is 2.005 in.**

C ffi i f E i


87/107

Material (m/m/C = 1 / C)

Glass 9 x 10 -6

Concrete 10 x 10 -6

Iron 12 x 10 -6

Brass 19 x 10 -6

Aluminum 25 x 10 -6

Coefficients of Expansion

T 9-1

H t C it


88/107

Heat Capacity

• The heat capacity of a material defines the amount

of energy that is needed to change its temperature.

The temperature change that will occur with a

given amount of energy.

H t U it


89/107

Heat Units

• Calorie (cal)

– The amount of heat required to raise thetemperature of one gram of water by one

degree Celsius.

• British Thermal Unit (BTU)

– The amount of heat required to raise the

temperature of one pound of water by onedegree Fahrenheit.

H t U it


90/107

Heat Units


91/107

Laws of Thermodynamics

1. Energy can neither be created or destroyed; the sum total of all

energy remains constant.

Q = U + W

Q - quantity of heat

U - change in internal energy

W - the work performed.


92/107

F 9-3 The first law of thermodynamics

Thermodynamics


93/107

2. Conversion of heat to work is limited by the temperature atwhich conversion occurs.

Wout

= QH - Q

L

QL - Quantity of heat from cold object.

QH - Quantity of heat from hot object.


94/107

F 9-4 Thermodynamic cycles

Thermodynamics


95/107

Heat Transfer

• Conduction: Energy transfer from a high temperatureregion to a low temperature region through a solid object.

• Convection: Energy transfer from a surface by the flowof a fluid over an object.

• Radiation: Electromagnetic radiation carries energyfrom one body to another.


96/107

F 9-5 Heat transfer by conduction

Heat Transfer


97/107

F 9-6 Heat transfer by convection

Heat Transfer


98/107

Fluid Power

Chapter 10


99/107

Fluid Dynamics

• Study of the flow of fluids:

– Velocity

– Pressure

– Force

That cause fluids to move


100/107

Density, , is the ratio of mass, m, to volume, V, of asubstance.

m

V

Specific Volume,

, is the volume occupied by a unit mass of substance.

1

Fluid Properties


101/107

Specific Weight, , is the force of gravity on a mass per unit

volume.

g

Specific Gravity, S, is the ratio of the density of substance to

the density of water.

S H O

2

H O g

cm2 31


102/107

F 10-1 Pressure definitions

Pressure

At h i P t


103/107

Atmospheric Pressure at

Sea Level

14.7 lb/in2

29.92 in. of Hg

76 cm of Hg

1.013 x 105 N/m2

Pa = N/m2

Pressurized Fluid in a


104/107

F 10-2 Pascal’s law

Pressurized Fluid in a

Sealed System

Principles of


105/107

Principles of

Fluid DynamicsConservation of mass is described by the continuity

equation:

A1v1 = A2v2

where A is the area that the fluid flows through, v is the

velocity of the fluid and the subscripts refer to the point

here the fluid enters and exits the system.


106/107

Conservation of energy is described by the energy

equation, also known as the Bernoulli equation:

where p is the pressure of the fluid and z is the elevation of

the system relative to a datum. It will be assumed that

flow is steady state and incompressible with a uniformvelocity profile.

v

g

p z

v

g

p z 1

2

11

2

2

22

2 2


107/107

Ciencias Fisicas e Ingenieriles

Documents

Transcript of Ciencias Fisicas e Ingenieriles