PHYSICS 11TODAY:

• Speed and Velocity Review• Problems/Worksheets

KINEMATICSThe Study of Motion

DISTANCEAs an object moves from one position to another, the length of the straight line

drawn from its initial to the final position is called:

POSITION• The shortest distance between the origin

and where the person is located• Vector quantity - has magnitude and

direction

DISPLACEMENTAs an object moves from one position to another, the length of the straight line

drawn from its initial to the final position is called:

DISPLACEMENT

Δ = a change in… = delta

DISPLACEMENT

Δd = a change between final and initial position

What was the dog’s DISTANCE travelled?

2

44

2

3

4

19 m

What was the dog’s DISPLACEMENT?

??

Calculating DISPLACEMENTA person is 2.0 m to the left of a viewpoint sign enjoying the view. She moves 4.5 m to the right

of the sign to get a better view. What is the person’s displacement?

6.5 m [right]

Calculating DISPLACEMENT

Practice Problems 2.1.1

Page: 39 – 40

Calculating DISPLACEMENT

503 m

a) What is the total distance the golf ball travelled while the golfer was playing the seventh

hole?

Calculating DISPLACEMENT

290 m, right

b) What is the Resultant Displacement of the Ball?

Speed

distance traveledaverage speed =

time of travel

equals to the object’s distance travelled over the time

interval It has NO DIRECTION,

only MAGNITUDE

Average Speed

distance traveledaverage speed =

time of travel

equals to the object’s total distance travelled over the

time interval It has NO DIRECTION,

only MAGNITUDE

total

Average Speedequals to the object’s total distance travelled over the

time interval It has NO DIRECTION,

only MAGNITUDE

Istantaneous Speedequals to the object’s speed at

the moment you are measuring the speed

Give me an example of when we are interested in measuring

instantaneous speed

Istantaneous Speedequals to the object’s speed at

the moment you are measuring the speed

DO YOU KNOW…What is a car’s average speed if the car makes a 100 km long trip from city A to city B if the first half of the trip is

driven at 50 km/h and the second half is driven at 100 km/h?

75 km/h 67 km/h

DO YOU KNOW…The average speed would be75 km/h if the car spent equaltime at 50 km/h and 100 km/h.

QUICK CHECK

Average speed is total distance over total time. Instantaneous speed is speed at a give point in time.

When an object is moving at a constant speed.

89 km/h

0.76 hr or 46 min

460 km

DO YOU KNOW…

What is the difference between:

speed average speed

instantaneous speed

DO YOU KNOW…

speed

average speed

instantaneous speed

Distance travelled over time

TOTAL Distance travelled over time

Speed of an object at a particular instant

•Constant speed•If the speed is not

changed over an extended period of

time

Uniform Speed???

Average VelocityThe total displacement of an object over the time interval during which

this displacement occurred is called:

Average Velocity

f iavg

f i

x xxv

t t t

average velocity = change in position

change in time =

displacement

time interval

SI Units: meters per second (m/s)

Average Velocity

average velocity = change in position

change in time =

displacement

time interval

SI Units: meters per second (m/s)

It has DIRECTION and MAGNITUDE

Think about it…A book is moved once around the edge of a tabletop with dimensions 1.75 m 2.25 m.

If the book ends up at its initial position, what is its

displacement?If it completes its

motion in 23 s, what is its

average velocity? What is its average

speed?

Think about it…A book is moved once around the edge of a tabletop with dimensions 1.75 m 2.25 m.

If the book ends up at its initial position, what is its

displacement?If it completes its

motion in 23 s, what is its

average velocity? What is its average

speed?

zero

zero

0.35 m/s

Think About it… Car A travels from Beijing to Shanghai at a speed 25 m/s. car B travels from Beijing to Xian at a speed 90

km/h

How do the velocities of the cars compare?

Velocities are not the same becausethey are travelling in different directions

You are on a skateboard and moving to the right covering 0.5 m each second for 10 seconds.

What is your velocity?

You are on a skateboard and moving to the right covering 0.5 m each second for 10 seconds.

What is your velocity?

0.5 m/s, right

Position – Time GraphsIf you know the object’s position at specific

times, you can determine its VELOCITY

Position vs. Time Graph If the VELOCITY is

constant, the graph of position vs. time is a straight line.

The slope indicates the VELOCITY

You are on a skateboard and moving to the right covering 0.5 m each second for 10 seconds.

What is your velocity?Doing this problem

GRAPHICALLY

You are on a skateboard and moving to the right covering 0.5 m each second for 10 seconds.

What is your velocity?

0.5 m/s, right

Slope = velocity

Graphing VelocityThe positions of three runners were recorded at specific

times. Here are their results:

Position vs. Time Graph

RUNNER 1

POSITION (km)

TIME (min)

0 0

5 10

10 21

15 29

20 40

RUNNER 2

POSITION (km)

TIME (min)

0 0

-5 8

-10 15

-15 25

-20 30RUNNER 3

POSITION (km)

TIME (min)

0 0

5 12

10 24

15 33

20 47

Describe the motion

represented by each graph

Graphing Velocity

0 5 10 15 20 25 30 35 40 45 50

-25

-20

-15

-10

-5

0

5

10

15

20

25

Positions of runners over time

Time (min)

Posit

ion

(k

m)

Graphing VelocityThe positions of three runners were recorded at specific

times. Here are their results:

Velocity = ?

RUNNER 1

POSITION (km)

TIME (min)

0 0

5 10

10 21

15 29

20 40

NEVER USE THE DATA POINTS TO CALCULATE THE SLOPE!!

Graphing Velocity

0 5 10 15 20 25 30 35 40 45 50

-25

-20

-15

-10

-5

0

5

10

15

20

25

Positions of runners over time

Time (min)

Posit

ion

(k

m)

Graphing VelocityThe positions of three runners were recorded at specific

times. Here are their results:

Velocity = slope

RUNNER 1

POSITION (km)

TIME (min)

0 0

5 10

10 21

15 29

20 40

𝟏𝟑−𝟑𝟐𝟓−𝟓

=𝟏𝟎𝟐𝟎

=𝟎 .𝟓𝟎𝒌𝒎 /𝒎𝒊𝒏

Graphing VelocityThe positions of three runners were recorded at specific

times. Here are their results:RUNNER 2

POSITION (km)

TIME (min)

0 0

-5 8

-10 15

-15 25

-20 30

Velocity = ?

Graphing Velocity

0 5 10 15 20 25 30 35 40 45 50

-25

-20

-15

-10

-5

0

5

10

15

20

25

Positions of runners over time

Time (min)

Posit

ion

(k

m)

Graphing VelocityThe positions of three runners were recorded at specific

times. Here are their results:

(−𝟕)−(−𝟒)𝟏𝟎−𝟓

=−𝟑𝟓

=−𝟎 .𝟔𝟎𝒌𝒎/𝒎𝒊𝒏

RUNNER 2

POSITION (km)

TIME (min)

0 0

-5 8

-10 15

-15 25

-20 30

Velocity = ?

Graphing VelocityThe positions of three runners were recorded at specific

times. Here are their results:

RUNNER 3

POSITION (km)

TIME (min)

0 0

5 12

10 24

15 33

20 47

Velocity = ?

Graphing Velocity

0 5 10 15 20 25 30 35 40 45 50

-25

-20

-15

-10

-5

0

5

10

15

20

25

Positions of runners over time

Time (min)

Posit

ion

(k

m)

Graphing VelocityThe positions of three runners were recorded at specific

times. Here are their results:

𝟏𝟓−𝟑𝟑𝟓−𝟖

=𝟏𝟐𝟐𝟕

=𝟎 .𝟒𝟒𝒌𝒎/𝒎𝒊𝒏

RUNNER 3

POSITION (km)

TIME (min)

0 0

5 12

10 24

15 33

20 47

Velocity = ?

HOMEWORK

Textbook:

pg. 44 – 47 #1, #3, #5, #7

Instantaneous VelocityIs a velocity of an object at some instant

(moment) at a specific point in the object’s path

Instantaneous VelocityEach moment a subject moves through

larger and larger displacements

If the VELOCITY is NOT constant, the

graph of position vs. time is a curve.

How can we find out the VELOCITY at

some exact time (3 sec)?

Instantaneous VelocityConstruct a STRAIGHT LINE which is TANGENT to the curve at that time

Instantaneous VelocityThe slope of that STRAIGHT LINE =

INSTANTANEOUS VELOCITY