1. The speed of an in-line skater is usually described in meters per second. The speed of a car is usually described in kilometers per hour.

2. Speed and Velocity
Speed- the distance traveled divided by the time taken to travel the distance.
formula: speed = distance/time (s=d/t)
units: meters per second (m/s)- standard SI unit, (km/hr), (cm/s)
A swimmer who swims 100 m in 56s
100 m ?
56s d d= s= t=
s t

3. A cyclist travels a total distance of 45 km at an average speed of 15 km/hr. How long did it take for him to go this distance?
45km
15 km/hr ? d d= s= t=
s t

4. An object in motion can change speeds many times as it moves from one point to another, speeding up or slowing down
Average speed- total distance traveled divided by total time taken
Constant speed- When an object covers equal distances in equal amounts of time.
A race car travels at a constant speed of 96 m/s means for every second the car goes exactly 96 meters.
Instantaneous speed- the rate at which an object is moving at a given instant in time.

5. Speed
The speedometer in a car measures the car’s instantaneous speed.
Note the scale markings are given both in km/h and miles per hour, mph.

6. Graphing motion
You can show the motion of an object on a line graph in which you plot distance verses time.
Slope- the steepness of a line on a graph
Calculating slope (pg .23)
Formula :
Unit of measure:

7. The slope of a line on a distance-time graph is speed
A steeper slope on a distance-time graph indicates a higher speed.

8. Graphing Motion

9. Graphing Motion

10. Graphing Motion

11. Velocity- speed of an object AND its direction of motion
Velocity is also a vector that shows changes in motion
Vectors of varying lengths, each vector corresponding to the velocity at a particular instant, can represent motion.
A longer vector represents a faster speed, and a shorter one a slower speed.
Vectors point in different directions to represent direction at any moment

12. Velocity
A cheetah’s speed may be as fast as 90 km/h. To describe the cheetah’s velocity, you must also know the direction in which it is moving.

13. Velocity
As the sailboat’s direction changes, its velocity also changes, even if its speed stays the same.

14. Assessment Questions
A woman jogs 10 kilometers in one hour, stops at a restaurant for one hour, and then walks 10 kilometers in two hours. What is her average speed for the outing?
0.2 km/h
4 km/h
5 km/h
10 km/h

15. Assessment Questions
A woman jogs 10 kilometers in one hour, stops at a restaurant for one hour, and then walks 10 kilometers in two hours. What is her average speed for the outing?
0.2 km/h
4 km/h
5 km/h
10 km/h ANS: C

16. Assessment Questions
Lisa plotted time on the x-axis of a line graph and distance on the y-axis. What does the slope of her graph represent?
total distance traveled
velocity
speed
displacement

17. Assessment Questions
Lisa plotted time on the x-axis of a line graph and distance on the y-axis. What does the slope of her graph represent?
total distance traveled
velocity
speed
displacement ANS: C

18. Assessment Questions
Lisa plotted time in seconds on the x-axis of a line graph and distance in centimeters on the y-axis. Her plot showed a straight line from (0,0) to (10, 20). What is the speed?
0.5 cm/s
2 cm/s
10 cm/s
20 cm/s

19. Assessment Questions
Lisa plotted time in seconds on the x-axis of a line graph and distance in centimeters on the y-axis. Her plot showed a straight line from (0,0) to (10, 20). What is the speed?
0.5 cm/s
2 cm/s
10 cm/s
20 cm/s ANS: B

20. Two velocities of an object are combined by using
Assessment Questions
Two velocities of an object are combined by using
division of the larger velocity by the smaller velocity.
addition of the two speeds.
vector addition.
numeric addition.

21. Two velocities of an object are combined by using
Assessment Questions
Two velocities of an object are combined by using
division of the larger velocity by the smaller velocity.
addition of the two speeds.
vector addition.
numeric addition. ANS: C

22. Assessment Questions
The SI unit for speed of an airplane is miles per hour. True False

23. Assessment Questions
The SI unit for speed of an airplane is miles per hour. True False
ANS: F, kilometers per hour