1. Speed Velocity Acceleration Freefall
Describing Motion
Speed
Velocity
Acceleration
Freefall

2. Speed Instantaneous speed Average speed Distance moved per unit time
Units
ms-1
kph
mph
cms-1
distance moved
time taken

3. Distance and speed are scalar quantities
Scalar Quantity
Magnitude
Number and unit
Always positive
Follows arithmetic rules
Vector Quantity
Magnitude and direction
May be positive or negative
Does not follow arithmetic rules

4. Vector Quantities Displacement Velocity Distance + direction
Displacement = final position – initial position
Velocity
Speed + direction
Average velocity =
displacement
time taken

6. Question Are the magnitudes of speed and velocity Alwaysssss the same
Sometimessssss the same
Neverrrrrr the same?

7. More questions
Page 34
Page 35, #s 1, 2 and 3

8. The velocity of a body is constant or zero if the forces are balanced.
Newton’s First Law
The velocity of a body is constant or zero if the forces are balanced.

9. Acceleration The rate of change in velocity Change in speed
Speeding up
Slowing down
deceleration
Change in direction
Both
Average Acceleration =
change in velocity
time taken

10. Questions, page 37

11. Graphs Displacement versus time Velocity versus time
Slope of the graph = average velocity
Velocity versus time
Slope of the graph = average acceleration
Area under the graph = distance traveled

12. Graphs

13. Example Who won the race? Who stopped for a rest?
How long did he stop for?
How long did Bob take to complete the race?
Calculate Albert's average speed.

14. Interpreting graphs
What is the greatest distance the object has traveled from its starting point?
What is the average speed of the object for time intervals:
0 to 2 min
2 to 6 min
2 to 7 min
0 to 8 min
Where is the object at the end of 8 min?

15. Speed and Acceleration
Choose the correct
words from the
following list to
describe the motion
during each part of the
journey
accelerating
decelerating
steady speed
stationary

16. Interpreting graphs What is the maximum velocity of the object?
Determine its average acceleration between
0 and 10s
10 and 30s
10 and 40s
0 and 40s

17. Force and Acceleration
Newton’s 2nd Law
If an unbalanced force acts on the body, then the body accelerates
Equation
acceleration =
force
mass

18. The Physics of Falling

19. The Physics of Falling Terminal Velocity Freefall
Motion where only gravity is acting on the body
Acceleration due to gravity, g
Air resistance is negligible
Terminal Velocity
The maximum speed of a falling object
When upward forces balance downward forces on the object

20. The Physics of Skydiving

21. The End