1. Frame of Reference, Speed, Velocity, Acceleration
Motion
Frame of Reference, Speed, Velocity, Acceleration

2. Motion Motion = change in position relative to a frame of reference
Something assumed to be stationary
Used to judge motion

3. Ways to measure motion:
Distance = how much change in position
(key words….how far)
Time = how long it took
(key words….how long)
Speed = how much distance is covered per unit of time (key words…..how fast)
Direction = N, S, E, W, Up, Down

4. Calculating Speed: Speed = distance per unit of time …..so
Time = distance/speed
Distance = speed * time
Units = cm/s m/s mi/hr km/hr

5. Average Speed for a trip
DO NOT add all the speeds and devide by how many there are!!!!!!!
DO total distance/ total time
(yes it will come out differently)
Try…..
Use average speed = total distance
total time

6. Calculate the average speed for the entire trip
Leg of Trip
Time (hours)
Distance covered
(km)
Speed for that Leg of the Trip
(km/hr)
First leg 2
150
Second leg 3
300
Layover 1
Third leg 4
200

7. Average speed = 650km/10hrs = 65km/hr NOT: (75 + 100 + 0 + 50 =225/4 = 56.25km/hr)
Leg of Trip
Time (hours)
Distance covered
(km)
Speed for that Leg of the Trip
(km/hr)
First leg 2
150
150/2 = 75
Second leg 3
300
300/3 = 100
Layover 1
Third leg 4
200
200/4 = 50
totals 10
650
650/10 = 65

8. Constant Speed Speed stays the same
Graph of distance vs. time is a straight line

9. Horizontal lines show…
No change in position so no distance covered but…
Time is passing so the object is…
Standing still speed = 0

10. Steeper lines show…. More distance covered per unit of time so..
faster speed.
A = slow B = stand still C = fast

11. Slope of distance time graph
Slope = rise so slope = distance
run time
distance = m so is speed
time S
Fast speed =
more distance in same time or
same distance in less time

12. Position vs. Time have Negative slopes
Negative slope means you are coming back toward the starting point.

13. Velocity = speed in a direction
25 m/s is a speed
25 m/s West is a velocity
Constant velocity = speed and direction stay the same.
If you go 50 mph around a race track..
Is this constant speed?
Is this constant velocity?

14. Velocities can be combined
Velocities in same direction ….
add
Velocities in opposite direction….
subtract

15. Acceleration How quickly speed changes
+ acceleration = increasing speed
- acceleration = decreasing speed
Acceleration = change in speed/time

16. Calculating Acceleration
Vi = initial velocity (starting speed)
Vf = final velocity (ending speed)
t = time it took for the speed to change
a = Vf-Vi t

17. Graphing Acceleration