1. 1-3 Average Speed: Following Distance and Models of Motion
WDYS? (p34) 1. 2. 3.
WDYT? (p34)
1.A safe following-distance between you and the next car is _____.
2.A safe following-distance has to take into account _____.

2. 1-3 Investigate (p34-36)
1-3 Investigate – use strobe photos to observe constant motion at different speeds
Sketch the “CAR” traveling 30mph diagram
Now, sketch the “CAR” traveling at 45mph and then again at 60mph…Were the images closer together OR farther apart???

3. 1-3 Investigate (p34-36)
3. Draw and Label each diagram: A= B= C=

4. Physics Talk:“Understanding Motion”(p37) Model 1: Using Strobe Photos
Speed  the distance traveled per unit of time (d/t)
Speed affects your following distance, braking distance, and total stopping distance
Constant Speed  speed that does NOT change over time, it stays the same
EXAMPLE The distance between the car images are evenly spaced out
Constant SLOW Speed  close together
Constant FAST Speed  farther apart

5. Speed and the Doppler (p44)
Part of safe driving is obeying the speed limit:
1. Read the speedometer
2. Use posted mile marker and measure the time
3. Sound of engine and tires
Doppler Effect  the change in pitch
1. Ambulance sirens
2. Police radar guns
3. Speed of galaxies huge distances from Earth

6. Reaction Distance (p46)
Reaction Distance  the distance that your car travels UNTIL you respond
***While you decide what to do, you need to remember that the car is still traveling over the ground***
A longer (slower) reaction time increases the distance you travel…therefore increases the chances of an accident

7. 1*3 TOTD 1. What is the correct word for:
ms _____ b) daL _____ c) hg _____
2. What is the correct symbol for:
a) centigram _____b) second _____ c) deciliter _____
3.Show ALL work for the following conversion:
37cg = _____g
1500ms = _____s
0.004kL = _____L
150hm = _____m

8. 1-3 Investigate (p34-36)
4. A motion detector measures the position of an object over a time interval and produces a GRAPH
a) c)
b) d)

9. 1-3 Investigate (p34-36)
5. Draw a graph depicting someone walking SLOWLY TOWARD the detector and then QUICKLY AWAY
6. Draw a MULTI-line graph where person 1 is walking slowly away and person 2 is walking quickly away

10. Physics Talk: “Understanding Motion”(p41-43) Model 2: Using a Graph
A second way to represent motion is with GRAPHS, where time is on the x-axis and distance on the y-axis
Anytime an object moves at a CONSTANT speed, the distance-time graph is a STRAIGHT line

11. Graphs: What’s happening?

12. Speed and the Slope of Distance-Time Graph
You compare speeds by looking at slopes
Slopes = Rise = (∆ y-axis)
Run (∆ x-axis)
Velocity = (∆d)
(∆t)
The steeper the slope, the faster the speed
The flatter the slope, the slower the speed

13. Physics Talk: “Understanding Motion”(p37-41) Model 3: Using an Equation
Average Speed  total distance traveled divided by the time it took to travel that distance
The Greek letter delta “∆” means “a change in” and is calculated by (final – initial)
Instantaneous Speed  the speed at any given moment, it is read on the speedometer
Velocity  speed WITH direction

14. Equations speed = distance / time v = d / t t = d / v d = v × t
It is very important to pay close attention to the units in your math work and answers!!!
speed = distance / time
v = d / t t = d / v d = v × t
Units for speed (v) : m/s km/h
time (t) : s h
distance (d) : m km

15. 1-3 Checking Up Questions (p46)
1. The average speed of a vehicle is different from instantaneous speed _____.
2. Speed and velocity of an object are different _____.
3. If the distance-time graph shows a straight & inclined line, the line represents _____.
4. A slow reaction time _____the distance you travel, therefore _____ the chances of an accident.

16. 1-3 PTG(p49 - 51) 1. a) b) 2. a) 3. 4. a) 5. 6. a) c) d)
7. a) b) c) 8. a) 9. a) 10. a) d) e) 11.