Physics Summary 2011

8/6/2019 Physics Summary 2011

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Physics/D'Amato/2011 End of year summary 1/4

0 General

A physical quantity is something about

the real world that you can measure.

Examples: distance, time, mass, velocity,

kinetic energy, etc

A unit of measurement is a standard

amount used to compare physicalquantities. Examples: meter, second,

kilogram, m/s, joule, etc.

Understand the difference between

making an observation, finding a pattern

in observations, and making a prediction

based on observations

Use a hypothesis to make a prediction of

what will be observed by experiment.

Devise an experiment which is capable

of disproving a hypothesis by showing

results that contradict the prediction

made by the hypothesis.

1 Kinematics

Different observers see the same motion

differently. Use the scope test.

Use a motion diagram and understand

the direction of change in motion

(acceleration)

Extract information about motion from

descriptions in words, graphs, tables,

and mathematics

Use precise language (includingcoordinate systems) to describe motion

quantitatively

Show that the quantity of velocity

characterizes the rate of change of an

object's position while acceleration

characterizes the rate of change of the

object's velocity

2 Dynamics

Use the quantity of force to represent an

interaction between two physical objects

Recognize when an object is inequilibrium: all forces exerted on it are

balanced by other forces

An object in equilibrium does not change

motion; an object in constant motion is

in equilibrium.


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Make and use a force diagram:

Choose an object of interest and

label it

Draw an arrow for each push or

pull and label it

Show the direction of the sum of

the forces

An object does NOT always move in the

direction of the sum of forces exerted on

it

An object ALWAYS changes motion in

the same direction as the sum of the

forces exerted on it; this means that if

the object is in equilibrium it may be at

rest or it may be moving at a constant

velocity

Check for consistancy between different

representations: the direction of change

in motion must be the same as the

direction of the sum of the forces

3 Circular motion

The quantity of "acceleration" includes

change in direction OR change in speed

An object moves in a circle at constant

speed only when there is a constant sum

of forces directed toward the center of

the circle

If there is a constant sum of forces

directed toward a single point, the object

will move in a circular path at constant

speed

4 Conservation and momentum

Understand and use the concepts:

system, environment, initial state, final

state, process.

"Constant" means that the quantity does

not change during a process

"Conserved" means that the total

amount of the quantity may change

during a process in some system, but

that the quantity does not appear from

nowhere or cease to exist. In other

words, there is always some choice of

system in which the quantity is constant.


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Momentum is a vector quantity with

magnitude and direction:

In a system that does not experience any

unbalanced interactions with its

environment, the total amount of

momentum in the system remains

constant; momentum is a conserved

quantity.

You can make and use a momentum bar

chart.

5 Work and energy

Recognize different forms of energy:

kinetic, gravitational potential, elastic

potential, electric potential, internal.

Positive work done on a system

increases the amount of energy in the

system; negative work decreases the

same quantity

Describe a process using an energy bar

chart and "energy story"

Recognize energy transformations

within a system and changes in system

energy caused by interactions with

objects outside the system

6 Light and vision

An object can be seen only when a light

ray from the object reaches your eye

Each point on an object sends light rays

in every direction

A smooth surface reflects a light ray at

the same angle on the opposite side of

the imaginary normal

Light rays travel in straight lines only in

the same medium; when going from air

to something else the ray bends toward

the normal and vice versa.

7 Electric forces

There are two types of electric charge,

positive and negative

Neutral objects contain equal amounts ofpositive and negative charge

Same-charged objects repel, oppositely-

charged objects attract

Negatively charged particles can move

freely inside conducting materials, but

their motion is limited in insulating

materials


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You understand why neutral objects are

attracted to charged objects

You understand why we believe charged

objects are NOT the same thing as

magnetic objects

8 Electric fields

An field is a model to understandinteraction at a distance

A charged object is the source of a field

that fills the space around it

A test object must be placed in the field

to detect the magnitude and direction of

the field at that location

The fields created by multiple source

charges combine at each point in space,

by the same rules we use to combine

other vector quantities

The direction of the electric field isshown in the direction of the force on a

positive test charge

The magnitude of the electric field at

some distance is

9 Electric circuits

Understand and use a complete circuit to

light a bulb

Recognize when two circuit components

are in parallel or in series

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Physics Summary 2011