Physics Reviewer Prelim

7/27/2019 Physics Reviewer Prelim

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PHYSICS

- Science of measurement

- Branch of science on the study of

nature

SYSTEM MEASUREMENT

Metric System SI( International)

English System BritishEngineering System

SI English

Length Meter (m) Foot (f)Mass Kilogram

(kg)Slug (sl)

Time Second (s) Second (s)

PREFIXES FOR SI UNITSPrefix Symbol Multiplier

Giga (9) G 1,000,000,000 =109

Mega (6) M 1,000,000 = 106

Kilo (3) k 1,000 = 103

Centi (-2)

c 0.01 = 10-2

Mili (-3) m 0.001 = 10-3

Micro (-6)

0.00000 = 10-6

Nano (-9)

0.00000000 =10-9

SIGNIFICANT FIGURES

- All non-zero digits are significant

- Zero may/may not be significant

- Those used to position the decimal

point are not significant

- To remove ambiguity use scientific

notation

*Ifeven nos.

2.25 -> 2.2 2.45 -> 2.4

*Ifoddnos.

2.35 ->2.4

*If the numbers are greater than 5

2.45 -> 2.5

Example:

4 Significant Figure; Proper SI form

1. 0.000002584 meter

Ans. 2.584 micrometer /

2.584

2. 9,763,560 byte

Ans. 9.764 gigabyte / 9.764

GB

CONVERSION OF UNITSLength

1m = 100cm = 1000 mm = 3.28 ft =

39.37 in

1cm = 10mm

1in = 2.54cm

1ft = 12in

1mi = 5280 ft = 1.61km

Time

1min = 60s

1hr = 60min = 360s

Mass1kg = 1000g = 2.205lb

1slug = 14.59kg

Volume

1L = 1000mL=1000cc(cm3, cubic

centimeter)

1ft3 =28.3L = 7.48 gal

1gal = 3.785L

1m3 = 1000L

1m3 = 35.3147 ft3

Accuracy- how close a measured value is to

the true/ accepted value

Precision

- how closely 2 or more

measurements agree with another

2 Errors

a. Systematic Error

- Affect the accuracy- One sided error

- Occur when a measuring device

is not properly working/

miscalibrated

- Difficult to detect but once

detected can be reduced by

refining the measurement

method or technique

b. Random Error

- Affect precision

- 2 sided

- Repeated measurements

fluctuate above and below the

value

Parallax Error


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- caused by incorrect position of

eye when reading a

measurement

Deviation

- difference between a measured

value and its mean or averagevalue

% Error measures accuracy of

measurement

% error = x 100

% Difference

% difference =

SCALAR & VECTOR QUANTITIES

Magnitude

- quantity of something

- a numerical value with units

Direction

- Which way is something

- North, East, West and South

- Describe in degrees

SCALAR QUANTITIES

- Only have magnitude

- No direction

- A numerical value with units

VECTOR QUANTITIES

- Magnitude and Direction

- Force and Velocity

Adding Vectors

Resultant/Vector Sum

- A single vector that is

equivalent to two or more

vectors

- We cannot add directly we

must condsider the

direction/magnitude

Rules

- Vectors acting in the same

direction

- Vectors acting in the opposite

direction (subtract)

- Follow the direction that has

the largest value

MECHANICS

- Focuses on motion and

causes motion to change

BRANCHES

Kinematics

- Describes motion

Dynamics

- Causes of motion

KINEMATICS

*Motion is relative

*Everything moves

Linear Motion

o Rectilinear

- Motion along astraight line

o Curvilinear

- Motion along a curved

path

Distance and Displacement

o Distance

- Is the length of a path

followed by a particle

o

Displacement- Is the straight line

distance from the

starting point to the

present location of

the particle

Speed and Velocity


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g = 9.8m/s2=

980 cm/s2 =

32.2 ft/s2

o Using Linear Motion

Equation

- We always assume

that acceleration is

constant

- We use vector

quantities not scalar

quantities

- Direction of a vector

is indicated by sign.

Incorrect use of sign

will result in incorrectanswers.

DYNAMICS

Force and Motion

o Force

is the cause of

motion

is a push or pull

Units

Newton (N)

dyne (dyn)

pound (lb)

o Net Force

the combination of

all forces acting on

an object

o Gravity Force (Weight)

Weight is the force of

a gravity on an

object

o Mass is the quantity of

gravity on an object

For

ce

Ma

ss

Acceler

ation

SI N kg m/s2

dyne

g cm/s2

English

lb slug

ft/s2

NEWTONS LAW OF MOTION

1. Law of Inertia (first law)

- Inertia is the natural

tendency of an object to

remain its current state of

motion

- Amount of an objects

inertia is directly related to

its mass

- Mass -> quantitative

measure of inertia;

quantity matter in an

object

2. Law of Motion(second law)

- A body acted upon by an

unbalanced force will

receive an acceleration

that isproportional to the

force and is in the direction

in which the force acts

3. Law of Interaction (third law)

- For every action forcethere is a reaction force,

equal in magnitude but

opposite in direction.

- Forces always come in

pairs equal and opposite

action reaction force pairs

NORMAL FORCE

- The support force exerted upon

an object that is in contact with

another stable object

Ex. A 35 kg crate rests on a horizontal

floor and a 65 kg person is standing on the

crate. Determine the magnitude of the

normal force

(a) The floor exerts on the crate

(b) The crate exerts on the floor


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FRICTION FORCE

- The force exerted by a surface as

an object moves across it or

makes an effort to move across it

COEFFICIENT of FRICTION ()

- The coefficient value is

dependentprimarily upon thenature of the surfaces that are in

contact with each other

FACTORS AFFECTING THEAMOUNT

OF FRICTION

1. The normal force

2. The materials from which the two

surfaces are made / relativeroughness of the surfaces in

contact (coefficient of friction )

Note: The frictional force is

independentof the speed and the

contact area between the objects.

CLASSES OF FRICTION FORCES

1. Static frictional force

- Exists when you start to move an

object from rest

-

2. Kinetic frictional force

- Exists while the object is moving

-

BASIC PRINCIPLES OF STATICS

STATICS

- is the study of forces acting on an

object

Torque and Equilibrium

o Torque

Is the tendency of a

force to rotate and

object about someaxis

= is the Torque

= is the lever arm

or moment arm

= is the force

o Net Torque

is the sum of all the

torques produced by

all the forces

Direction

Counterclockw

ise negative

Clockwise

positiveo Static Equilibrium

Occurs when an

object is at rest,

neither rotating nor

translating

Conditions

Transitional

Equilibrium or

Force Law of

Equilibrium

Rotational

Equilibrium or

Moment of Law

of Equilibrium

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Physics Reviewer Prelim