ENGR 34 Statics Chapter 1, Day 1 Intro

1

ENGR 34 STATICS

Vince Bertsch627 Analy Village

527-4621vbertsch@santarosa.edu

Pick up handouts and workbook from the front table a) Define mechanics & statics

b) Overview of the course logistics and resourcesc) Review units and vectorsd) Recap Newton’s Laws

Today’s Objectives

WHAT IS MECHANICS??•The study of what happens to a “thing”

when it gets “pushed”

WHAT IS STATICS??•The study of what happens to a “thing”

when it gets “pushed” but doesn’t accelerate

BRANCHES OF MECHANICS

Statics(no change in motion)

Dynamics(acceleration)

Rigid Bodies(don't change shape)

Deformable Bodies(do change shape)

Incompressible(hydrodynamics)

Compressible(aerodynamics)

Fluids

Mechanics(study of push on things)

Why do we care about statics? Why do we care about statics?

ENGR 34 Statics Chapter 1, Day 1 Intro

2

COURSE GOALS• Foundational knowledge of statics• Analytical problem solving skills• Calculator and computer skills• Working together• Free body diagrams• # of equations, # of unknowns

COURSE MATERIALS• Hibbeler, Engr. Mechanics Statics, 14th Ed

• Course workbook

• Mastering EngineeringMasteringEngineering.com

• My homepage profiles.santarosa.edu/vince-bertsch

• Course websitecanvas.santarosa.edu/courses/17349

Engr 34 Statics

Workbook

ESTIMATING UNIT CONVERSIONS

•1 m ≈ 3 ft•1 km ≈ 0.6 mi•25 mm ≈ 1 in

•1 kg ≈ 2 lb•10 N ≈ 1 kg

Just multiply or divide by 10 or 2.•1000N ≈ 1 vb

Estimating PracticeNo calculatorsFill in the table with estimated values in the other units.

pounds kilograms newtons

143

3241

22

ESTIMATING PRACTICE

VECTOR REVIEWVectors have both a magnitude and a direction.

Vector variable names: AB or F AB or F

Unit vectors: i, j, k, x, y, z, AB, F, i,j,k, e

Force values: F = 10#<100° (uses default defn for angle)F = 40 N 80° (uses picture to define angle)F = 10 lb T (uses default object tension defn)F = 15N (magnitude only, use arrow in diagram

for both direction and +/- significance)

^ ^ ^ ^ ^ ^ ^ ^ ^

2D COORDINATE CONVERSIONApproach #1 (manual):

Keep angles between 0 and 90,

sin for opposite, cos for adjacent,

do signs yourself.

Approach #2 (automatic):

Use standard defined angles,

(from x axis counter-clockwise),

input into calculator.

ENGR 34 Statics Chapter 1, Day 1 Intro

3

2D COORDINATE PRACTICE

2D Coordinate Conversions

30°X

Y

A5

A

Ay

x=

=

Write the trigonometric relationships, do not solve.

40°

=yB

xB =

Y

X9

B

C =

Y

7

or

or

50°

C

5cos(30°)

5sin(30°)

-9sin(40°)

-9cos(40°)

9cos(-130°)

9sin(-130°) 7/sin(40°)

NEWTON’S LAWS

I F=0 iff no change in motion

II F = ma

III Equal & Opposite

For Next Time:• Register for MasteringEngineering.com• Bring Calculator• Bring Workbook