1. Describing Motion Motion Speed & Velocity
Motion & Forces
Describing Motion
Motion
Speed & Velocity

2. Newton’s First Law
Newton’s First Law of Motion

3. Motion
Problem:
Is your desk moving?
We need a reference point...

4. Motion
Motion -
Reference point
Motion

5. Relative Motion .

6. Motion
Distance .

7. Motion
Displacement .
. Example – What is your displacement in a school day ?

8. Motion
Displacement is the distance and direction of an object's change in position from a reference point.
Suppose a runner jogs to the 50-m mark and then turns around and runs back to the 20-m mark.
The runner travels 50 m in the original direction (north) plus 30 m in the opposite direction (south), so the total distance she ran is 80 m.

9. 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 forward. .

10. s d t
Speed & Velocity
Speed .

11. Calculating Speed .

12. Calculating Speed

13. Speed & Velocity
Instantaneous Speed .
Average Speed

14. Changing Instantaneous Speed
When something is speeding up or slowing down,
If an object is moving with constant speed,
To determine direction you need to know the velocity

15. Speed & Velocity Problem:
A storm is 10 km away and is moving at a speed of 60 km/h. Should you be worried? .

16. Speed & Velocity
Velocity .

17. t d s Calculations d = 100 m s = t = 20 s s = ? GIVEN: WORK:
Your neighbor skates at a speed of 4 m/s. You can skate 100 m in 20 s. Who skates faster?
GIVEN:
d = 100 m
t = 20 s
s = ?
WORK:
s = s d t

18. t d s Calculations s = 330 m/s t = d = 1km = 1000m t = ? WORK: GIVEN:
Sound travels 330 m/s. If a lightning bolt strikes the ground 1 km away from you, how long will it take for you to hear it?
GIVEN:
s = 330 m/s
d = 1km = 1000m
t = ?
WORK:
t = s d t

20. Graphing Motion slope = steeper slope = Straight line = flat line +*
07/16/96
Graphing Motion
slope =
steeper slope =
Straight line =
flat line +
Single point =
Distance-Time Graph A B *

21. Graphing Motion Who started out faster? . Who had a constant speed?
Describe B from min.
Find their average speeds.
Distance-Time Graph A B

22. Graphing Motion
Distance-Time Graph .
Changing slope =

23. Graphing Motion Specify the time period when the object was...
slowing down .
speeding up
moving at a constant speed
not moving
Speed-Time Graph