Unit 1: Linear Motion Sprayberry Physics. 2 Physics Comp Book UNIT 1: Linear Motion (@top, BIG!) p....

Unit 1: Unit 1: Linear MotionLinear Motion

Sprayberry

Physics

2

Physics Comp BookUNIT 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:

How to remember:

Drawing:

Motion in a straight line

linear motion

vertical horizontal

What it’s NOT:

4

Concept Map: Linear Motion p. 2

when an object moves we observe—

The position changing

How quickly the position changes

The rate at which the movement changes

called

called

called

called

called

which is

calculated by

which is

calculated by

which is

calculated by

which is

calculated by

which is

calculated by

5

When an object moves, we can observe:

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

For your concept map on p.2 of comp book!

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 & Displacement

B

A

C

5 m

4 m

3 m

Your distance traveled is 7m

You walk from A to B to C.What is your distance traveled?What is your displacement from A?

Your displacement form A is 5 m

9

Let’s do Frayers for distance & displacement in your comp book:

Definition:

Don’t confuse this with:How to remember:

How to calculate:

10

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

Types of Speed

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?

Average speed total distance

total time

Speed d

t

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

Average velocity total displacement

total timeV

x

t

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

t

xx

tt

xx

t

xV if

if

ifaverage

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:

Definition:


How to calculate:

Wait for the next slide

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)

(1) LIST (3) Equation

(2) LABEL w/units (4) Solve

Average speed 140 miles

2 hour 2 hour

Average speed 140 miles

4 hours35 mph

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

150 Km/hr

100 Km/hr

50 Km/hr

North

North

40º North of East

22

How fast is the plane moving in respect to the ground? 100 Km/hr

Wind35 Km/hr

Velocity Example 2

23

How fast is the plane moving in respect to the ground?

Notice the two velocities are occuring in the same LINE (linear motion…)

100 Km/hr

Wind35 Km/hr

Result

65 Km/hr

Velocity Example 2

24

Is this linear motion?


100 Km/hr

50 Km/hrWind

Velocity Example 3

25


100 Km/hr

50 Km/hrWind

Resultant

a2

b2c2

a2 b2 c2+ =

Velocity Example 3

26


100 Km/hr

50 Km/hrWind

Resultant

a2

b2c2

a2 b2 c2+ =

R2 = (100)2 + (50)2 R2 = 10,000 + 2500 R2 = 12,500R = 111.8 Km/hr

Velocity Example 3

27

Concept Map: Linear Motion p. 2

when an object moves we observe—

The position changing

How quickly the position changes

The rate at which the movement changes

called

called

called

called

called

which is

calculated by

which is

calculated by

which is

calculated by

which is

calculated by

which is

calculated by

Adding all the legs of the journey

distance

displacement

speed

velocity

acceleration

Xfinal –x initial

Total distanceTotal time

xfinal –x initial

time

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

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

Place these words in the correct space on the diagram:

33

Acceleration Change in velocity divided by the change in

time

a Vt

34

Acceleration

Great animation showing acceleration:http://www.physicsclassroom.com/mmedia/kinema/acceln.cfm

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


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


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:

Definition:


How to calculate:

Wait for the next slide

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?



41


A car is said to go "zero to sixty in six point seven seconds". What is its acceleration in m/s2?



42


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)?



Unit 1: Linear Motion Sprayberry Physics. 2 Physics Comp Book UNIT 1: Linear Motion (@top, BIG!) p....

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