1. Motion
S8P3. Students will investigate relationship between force, mass, and the motion of objects.
a. Determine the relationship between velocity and acceleration.

2. Measuring Motion Motion Speed & Velocity Acceleration

3. Motion
Motion is when an object changes position over time relative to a reference point.
Problem:
Is your desk moving?
We need a reference point...
a nonmoving or moving point from which motion is measured

4. Motion Superman Example
The speeding bullet is a moving reference point to Superman’s motion.
The tall building is the non-moving reference point when Superman leaps.

5. Motion Motion Change in position in relation to a reference point.

6. Motion
Problem:
You are a passenger in a car stopped at a stop sign. Out of the corner of your eye, you notice a tree on the side of the road begin to move.
What’s the problem?
You have mistakenly set yourself as the reference point.

7. s d t Speed Speed rate of motion
distance traveled by an object in a given amount of time
Write Formula

8. Speed Instantaneous Speed speed at a given instant Average Speed
Write Formula

9. Speed
Problem:
A storm is 10 km away and is moving at a speed of 60 km/h. Should you be worried?
It depends on the storm’s direction!

10. Velocity Velocity speed of an object in a given direction
changes when speed and/or direction changes
Examples:
The car’s velocity was 104 km/h N (about 65 mph N).
John’s velocity was 1 m/s S (about 2.2 mph S)
The runner’s velocity was 37 km/h W (about 23 mph W).

11. Graphing Motion slope = speed steeper slope = straight line =*
07/16/96
Graphing Motion
Distance-Time Graph A B
slope =
steeper slope =
straight line =
flat line =
speed
faster speed
constant speed
no motion *

12. Graphing Motion Who started out faster? A (steeper slope)
Distance-Time Graph A B
Who started out faster?
A (steeper slope)
Who had a constant speed? A
Describe B from min.
B stopped moving
Find their average speeds.
A = (2400m) ÷ (30min) A = 80 m/min
B = (1200m) ÷ (30min) B = 40 m/min

13. t a Acceleration Acceleration the rate of change of velocity
vf - vi t
Acceleration
the rate of change of velocity
change in speed and/or direction
Write Formula
a: acceleration
vf: final velocity
vi: initial velocity
t: time

14. Acceleration The velocity can change even when the speed is constant!
Examples:
25 m/s S  25 m/s E
55 m/s W  20 m/s W

15. Acceleration Positive acceleration “speeding up” Ex. 5 km/h  25 km/h
Negative acceleration (Deceleration)
“slowing down”
Ex. 25 km/h  5 km/h

16. Acceleration

17. Graphing Motion
Distance-Time Graph
Acceleration is indicated by a curve on a Distance-Time graph.
Changing slope = changing velocity

18. Graphing Motion slope = acceleration
Speed-Time or Velocity-Time Graph
slope = acceleration
“+” velocity = speeds up
“-” velocity = slows down
Straight line = constant acceleration
flat line = constant speed

19. Graphing Motion Specify the time period when the object was...
Speed-Time or Velocity-Time Graph
Specify the time period when the object was...
slowing down
5 to 10 seconds
speeding up
0 to 3 seconds
moving at a constant speed
3 to 5 seconds
not moving
0 & 10 seconds