Chapter One Motion

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14 Νοε 2013 (πριν από 3 χρόνια και 10 μήνες)

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Chapter One

Motion

Mrs. Swanson

I. Describing Motion


A. Describing Motion
-


An object is in motion if its distance
from another object is changing.

B. Reference Point


A place or object used for
comparison. An object is in motion
if…it changes position relative to a
reference point. (
ie
. Tree, sign,
building)

C. Relative Motion


Depends on the reference point you
choose


D. Measuring Distance


SI Units


International Units of
Measure


A. Length
-

Meter, Centimeter,
Millimeter.


B. Converting Units Math Skills
-

1,000mm

or
100 cm

1m




1m


Measuring Distance


Meter


= 50 m

1 mm

international unit for measuring
distance.

Speed and
Velocity

Measuring motion

E. CALCULATING SPEED
-


The distance an object travels in
a certain amount of time, you
can calculate the speed of the
object.


Units for speed


Depends…



but will always be a distance unit /
a time unit


Examples:

mi./h

km/h

cm/s

m/s


Cars:


Jets:


Snails:


Falling objects:

Calculating speed


If I travel 100 kilometer in one hour
then I have a speed of…


100 km/h



If I travel 1 meter in 1 second then
I have a speed of….


1 m/s

1.
The speed Equation

2.
S
= d/t

2. Average speed


Speed is usually NOT CONSTANT


Examples:


Cars stop and go regularly


Runners go slower uphill than
downhill



Average speed

=



total distance
traveled/total
time it took.

Calculating Average Speed


It took me 1 hour to go 40 km on the
highway. Then it took me 2 more hours to
go 20 km using the streets.


Total Distance:


40 km + 20 km = 60 km


Total Time:


1 h + 2 h = 3 hr


Average Speed:




3. Instantaneous Speed


Rate at which an object is moving
at a given instant in time

Question


I ran 1000 m in 3 minutes. Then
ran another 1000 m uphill in 7
minutes. What is my average
speed?


A) 100 m/min


B) 2000 m/min


C) 10 m/min


D) 200 m/min


E) 20 m/min

Total Dist. =
1000 m + 1000 m =
2000 m


Total Time =
3 min + 7 min =
10 min


Average
speed =
total
distance/total
time
=


2000m/10 min
=

200 m/min

4.
DescribingVelocity


Velocity




the SPEED and
DIRECTION of an object.

“Speed in a given direction”


Example:


Airplane moving
North

at 500 mph


Missile moving
towards you
at
200m/s

Question


What is the difference
between speed and velocity?



Speed is just distance/time.
Velocity includes direction as
well.

F. Graphing Motion


Distance vs. Time on a line graph


1. y axis vertical


2. x axis horizontal


3. steepness of the line


Slope=
Rise



Run


http://www.phschool.com/webcodes10/index.cfm?fu
seaction=home.gotoWebCode&wcprefix=cgp&wcsuff
ix=3011





II. Acceleration

A. Definition
-

The rate at which
velocity changes. “The process of
speeding up”

1. Increasing Speed= The object
accelerates

2. Decreasing Speed= Negative
Acceleration

3. Changing Direction= Object that is
traveling at a constant speed can
still be accelerating.


B. Calculating Acceleration


Change in speed over time


Acceleration =
Final speed
-

Initial
Speed







Time


C. Graphing Acceleration


1. Speed versus time
-


Slope=
Rise



Run


2. Distance versus time graph