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The term uniform motion describes an object that moves at a constant

rate in the same direction.

True uniform motion is nearly impossible to maintain in real life

situations.

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5.0 m

t = 1.2 s

The car moved a distance of 5.0 m in a time of 1.2 s. It did not exhibit

uniform motion because it sped up and slowed down.

The average speed of the car is defined as a change in distance during a

time interval.

avgdvt

=

vavg = average speed

(m/s)d = distance travelled

(m)t = time elapsed (s)

The is the greek letterdelta and means change in.

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Practice Problems p.

128

1) A huge ocean wave, or tsunami, travels a distance of 4.0 106 m

in 3.6 104 s. Calculate the average speed of the tsunami.

1.1 102

m/s

2) A Concorde airplane could fly at an average speed of 694 m/s.

Calculate how long it would have taken the Concorde to fly around

the world, which is approximately 4.00 107 m.5.76 104

s

3) An electric train is travelling at an average speed of 6.9 m/s for 4.0 s.

Calculate the distance travelled by the train.

28 m

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0

10

20

30

40

50

0.0 2.0 4.0 6.0 8.0 10.0

Distance vs Time

Distance(m)

Time (s)

Time

t (s)

Distance fromFirst Marker

d (m)

0.0 0

2.0 10

4.0 20

6.0 30

8.0 40

10.0 50

A motorboat is travelling at a constant speed. A person on the shore is

recording the distance the boat travels away from the first marker buoy

every 2.0 s.

text p.129

A distance vs time graph can be plotted to

analyze the motion of the boat.

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0

10

20

30

40

50

0.0 2.0 4.0 6.0 8.0 10.0

Distance vs Time

Distanc

e(m)

Time (s)

slop

e

rise=

run

y=

x

change in

distance

change

in time

average speed=

distance

time

avg

dv

t

=

The slope of a line on a distance-time graph

is equal to the average speed of the object.

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0

10

20

30

40

50

0.0 2.0 4.0 6.0 8.0 10.0

Distance vs Time

Distanc

e(m)

Time (s)

(0,0) (6.0,30)

( )

( )2 1

2 1

y yslope

x x

=

( )

( )

30 0

6.0 0

m

s

=

= 5.0

m/s

So, the boat is moving at a constant rate of

5.0 m/s.

Dont forget to

round to the right

number of sig

digs, baby!

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Distance vs

Time

Distan

ce

(km)

Time

(h)

12

3

The graph shows the motion

of three different cars.

text p.130

Car 1 is travelling at a constant speed, faster than car 2 (slope is

steeper).Car 2 is travelling at a constant speed, slower than car 1 (slope is

not as steep).

All three cars have a constant

speed, because the slope of

their line does not change.

Car 3 is stopped. The slope is zero, therefore the speed is zero.

The distance does not change as time passes.

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read pages 126 130

Practice Problem 4, p.130 (use graph paper)

Extra problems worksheet 1 7

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Time WhenBoat Passes

Marker

t (s)

Speed of the Boatas it Passes Each

Marker

v (m/s)

0.0 5.00

2.0 5.00

4.0 5.00

6.0 5.00

8.0 5.00

10.0 5.00

text p.131 0.00

1.00

2.00

3.00

4.00

5.00

6.00

0.0 2.0 4.0 6.0 8.0 10.0

Speed vs Time

Speed(m

/s)

Time (s)

The boat is exhibiting uniformmotion, so that means the speed does

not change.

A horizontal line has a slope of

zero, and that means that the

speed stays constant as time

passes.

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The slope of a line on a speed-time graph indicates

that an object is either speeding up or slowing down.

Speed vs

Time

Speed

(m/s

)

Time

(s)

A

B

text p.131

Object A is increasing its speed (positiveslope).

Object B is decreasing its speed

(negative slope).

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The area under the line of a speed-time graph

determines the distance the object travels.

Speed vsTime

Speed

(m/s)

Time

(s)

5.0

1

0

A boat is travelling at a rate of 10 m/s

for 5.0 s.

The area under the line forms a

rectangle.area = length x

width( )

m10 5.0 s

s

=

= 50

m

The boat travels a distance of

50 m.

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read pages 130 133

Practice Problem 5, p.133

B1.1 Check and Reflect

page 135 #s 1 13