1. Unit 1: Linear Motion
Mrs. Jennings
Physics

2. Physics Comp Book UNIT 1: Linear Motion (@top, BIG!) p. 1
Copy GPS listed on the LTA. Circle the verbs; underline the nouns.
Page Contents
2 Concept Map: Linear Motion pt. 1
3 linear motion, distance
4 displacement, speed
5 velocity, acceleration
6 Venn Diagram: Scalar vs. Vector
7 Concept Map: Linear Motion pt. 2
8 Lab SUMUPS:
* Distance vs. Displacement
* Froggy

3. Let’s do a Frayer model for linear motion:
Definition:
Drawing:
Motion in a straight line
linear motion
vertical
horizontal
What it’s NOT:
How to remember:

4. Concept Map: Linear Motion p. 2 when an object moves we observe—
which is calculated by
called
The position changing
How quickly the position changes
The rate at which the movement changes

5. When an object moves, we can observe:
For your concept map on p.2 of comp book!
The position changing
Distance: how far it travels is called (in meters)
Displacement: how far its position is from the starting point (in meters with a direction)
How quickly the position changes
Speed: how fast it’s covering distance
(or how much distance is covered in an amount of time)
Velocity: how fast it’s position is moving and in what direction relative to some other point (like home or a destination
The rate at which the movement changes
Acceleration: is it speeding up or slowing down

6. Displacement Isn’t Distance
The displacement of an object is not the same as the distance it travels
Example: Throw a ball straight up and then catch it at the same point you released it
The distance is twice the height
The displacement is zero

7. Distance & Displacement

8. Distance & DisplacementB
4 m
5 m
3 m
You walk from A to B to C.
What is your distance traveled?
What is your displacement from A? A
Your distance traveled is 7m
Your displacement form A is 5 m

9. Let’s do Frayers for distance & displacement in your comp book:
How to calculate:
Definition:
How to remember:
Don’t confuse this with:

10. Types of Speed
Instantaneous Speed is the speed at any specific instance or moment in time
Ex. On a speedometer reading…
you are traveling 35 mph (mi/hr)
or 50 km/h or 25 m/s
Average Speed is the total distance covered divided by total time

11. How do you calculate average speed?
The average speed of an object is defined as the total distance traveled divided by the total time elapsed
OR take the average:
(initial speed + final speed) 2
Speed is a scalar quantity
… why is it not a vector?

12. Speed, cont
Average speed totally ignores any variations in the object’s actual motion during the trip
The total distance and the total time are all that is important
SI units are m/s

13. Speed & Velocity Speed is the distance traveled in a certain time.
Velocity is the displacement traveled in a certain time.
Velocity is speed in a given direction.

14. Velocity
The average velocity of an object is defined as the total displacement traveled divided by the total time elapsed
Velocity is a vector quantity

15. Velocity It takes time for an object to undergo a displacement
The average velocity is rate at which the displacement occurs
generally use a time interval, so let ti = 0

16. Velocity, cont.
Direction will be the same as the direction of the displacement (time interval is always positive)
+ or - is sufficient to indicate direction
Units of velocity are m/s (SI), cm/s (cgs) or ft/s (US Cust.)
Other units may be given in a problem, but generally will need to be converted to these

17. Speed vs. Velocity
Cars on both paths have the same average velocity since they had the same displacement in the same time interval
The car on the blue path will have a greater average speed since the distance it traveled is larger

18. Let’s do Frayers for speed & velocity in your comp book:
How to calculate:
Definition:
Wait for the next slide
How to remember:
Don’t confuse this with:

19. Speed vs. Velocity You drive from Yakima to Seattle (140 miles away)
You stop in Ellensburg for a 2 hr lunch with a friend.
Your total driving time is 2 hours
What is the average speed?
What is the average velocity?
(solve these questions in the Frayers)
LIST (3) Equation
(2) LABEL w/units (4) Solve

20. Constant Velocity Constant velocity is constant velocity
The instantaneous velocities are always the same
All the instantaneous velocities will also equal the average velocity

21. Velocity Example 1
North
North
40º North of East

22. How fast is the plane moving in respect to the ground?
Velocity Example 2
How fast is the plane moving in respect to the ground?

23. Velocity Example 2
How fast is the plane moving in respect to the ground? Notice the two velocities are occuring in the same LINE (linear motion…)

24. Velocity Example 3
Is this linear motion? How fast is the plane moving in respect to the ground?

25. How fast is the plane moving in respect to the ground?
Velocity Example 3
How fast is the plane moving in respect to the ground?

26. How fast is the plane moving in respect to the ground?
Velocity Example 3
How fast is the plane moving in respect to the ground?

27. Concept Map: Linear Motion p. 2 when an object moves we observe—
which is calculated by
called
The position changing
distance
displacement
speed
velocity
acceleration
Adding all the legs
of the journey
Xfinal –x initial
Total distance
Total time
How quickly the position changes
xfinal –x initial
time
The rate at which the movement changes
vfinal –v initial
time

28. Scalar vs. Vector Scalar - magnitude only and units
(e.g. volume, mass, time, speed, distance)
magnitude means SIZE,
units: like meter, mile, etc.
Vector – magnitude, units & direction (e.g. weight, velocity, acceleration)
in other words:
where is this “thing” pointing?

29. Pictorial Representation
An arrow represents a vector
Length = magnitude (size) of vector
Direction = direction of vector

30. Pictorial Representation
This arrow could represent a vector of magnitude 10 point to the “right”
This arrow could represent a vector of magnitude 5 point to the “left”

31. Get your comp book…
Draw an empty Venn Diagram like this on p. 6

32. Label one side scalar, other vector
Place these words in the correct space on the diagram:
Magnitude
Size
Direction
Units
Distance
Displacement
Speed
velocity
Acceleration
Mass
Weight
12 cm
47 kg (mass)
470 Newtons (weight)
50 meters
50 meters West
25 m/s
25 m/s toward home
25 m/s away from home
10 m/s2
10 m/s2 toward the ground

33. Acceleration
Change in velocity divided by the change in time

34. Acceleration Great animation showing acceleration:
Changing velocity (not constant) means an acceleration is present
Acceleration is the rate of change of the velocity (how fast the velocity changes)
Units: m/s2 (SI)
other examples: cm/s2
ft/s2

35. Average Acceleration Vector quantity
When the sign of the velocity and the acceleration are the same (either positive or negative), then the speed is increasing
When the sign of the velocity and the acceleration are in the opposite directions, the speed is decreasing

36. Relationship Between Velocity & Acceleration
Uniform velocity (shown by red arrows maintaining the same size)
Acceleration equals zero

37. Relationship Between Velocity & Acceleration
Velocity and acceleration are in the same direction
Acceleration is uniform (blue arrows maintain the same length)
Velocity is increasing (red arrows are getting longer)
Positive velocity and positive acceleration

38. Relationship Between Velocity & Acceleration
Acceleration and velocity are in opposite directions
Acceleration is uniform (blue arrows maintain the same length)
Velocity is decreasing (red arrows are getting shorter)
Velocity is positive and acceleration is negative

39. Let’s do a Frayer for acceleration in your comp book:
How to calculate:
Definition:
Wait for the next slide
How to remember:
Don’t confuse this with:

40. Acceleration Example 1
(solve this problem in the Frayer section…)
A car is moving at a speed of 35.8 m/s. If it takes 2.0 s to come to a complete stop, what acceleration would it have?
LIST (3) Equation
(2) LABEL w/units (4) Solve

41. Acceleration Example 2
A car is said to go "zero to sixty in six point seven seconds". What is its acceleration in m/s2?
LIST (3) Equation
(2) LABEL w/units (4) Solve

42. Acceleration Example 3
The driver from the previous problem can't release his foot from the gas pedal. (The gas pedal is also known as the accelerator. Coincidence? I think not.) How many additional seconds would it take for the driver to reach 80 mph? (assuming the acceleration hasn't changed)?
LIST (3) Equation
(2) LABEL w/units (4) Solve