1. motion

2. How can we tell if an object has moved??

3. Motion and Position
Motion: when an object changes its position relative to a reference point
Frame of Reference: a coordinate system in which the position of the objects is measured
Reference Point: where the x-axis and the y-axis of the frame of reference intersect

4. Distance vs. displacement
Distance: how far an object has moved
Displacement: the distance and direction of an object’s change in position from the starting point

5. Distance vs. displacement
Can the displacement of an object every be more than the distance an object traveled?

6. Calculating displacement
A squirrel runs 4.8 m across a lawn, stops and runs 2.3 m back in the opposite direction. What is the squirrels displacement from its starting point?
Displacement = 4.8 m – 2.3 m = 2.5 m

7. Calculating displacement
A cyclist leaves home and rides due east for a distance of 45 km. She returns home on the same bike path. What is her displacement?
Displacement = 45 km – 45 km = 0 km

8. speed Speed: the distance an object travels per unit time
Speed (s) = distance (d) / time (t)

9. Speed Speed = distance traveled time taken metres
Metres per second (m/s)
seconds

10. Speed Speed = distance traveled time taken kilometres
Kilometres per hour (km/h)
hours

11. Units of speed Unit of Speed Examples of Uses Approximate Speed km/s
Rocket escaping Earth’s atmosphere
11.2 km/s
km/h
Car Traveling on the highway
100 km/h
cm/yr
Geologic Plate Movement
2 cm/year – 17 cm/yr

12. Practice calculating speed
A car traveling at a constant speed covers a distance of 750 m in 25 s. What is the car’s speed?
Distance = 750 m
Time = 25 s
s = d/t
750/25 = 30 m/s

13. Distance traveled
What if we know the speed of an object and the time it moved for and need to calculate the distance traveled?
speed = distance/time
Distance = speed x time

14. calculating distance traveled
Mrs. Cowley’s drive to work takes her 30 minutes. If she drives at an average speed of 80 km/h, what is the distance between the school and her house?
d = s x t
d = 80 km/h x .5 h
d = 40 km

15. Motion with constant speed
Constant Speed: no acceleration or deceleration occurs
Average Speed: the speed of motion when speed is changing over time
Instantaneous speed: the speed at a given point in time

16. Learning check
What are 2 examples of motion in which the instantaneous speed changes?

17. Graphing motion
Distance-time graph: shows the motion of an object over a period of time
Time is plotted on the x-axis
Distance is plotted on the y-axis

18. Graphing motion Straight line: the object moves with a constant speed
Steeper slope = faster movement
Horizontal line = object is at rest

19. Graphing motion
Curved lines: to the right = getting slower, to the left = getting faster

20. Velocity
Velocity: includes the speed AND direction of an object

21. Acceleration Acceleration: the rate of change of an objects velocity
Acceleration occurs when an object changes speed, direction or both

23. Acceleration Equation
a = Vƒ - Vί t
a = acceleration
Vί = initial velocity
Vƒ = final velocity
t = time

24. Practice Problem
A plane stars at rest on a runway. After 20 seconds the speed of the plane is 80 m/s. Calculate the acceleration of the plane.
a = Vƒ – Vί t
a = 80 m/s – 0 m/s
20 s
a = 4 m/s

25. Practice Problem
A skateboarder is slowing down to a stop. He is moving at a speed of 3 m/s. He comes to a stop in 2 seconds. Calculate the skaters acceleration.
a = Vƒ – Vί t
a = 0 m/s – 3 m/s
2 s
a = -1.5 m/s