Admit Ticket/Exit Ticket (3) Cornell Note Sheets€¦ · The Need for Speed! • Speed is one type...

Items to pick-up: Admit Ticket/Exit Ticket (3) Cornell Note Sheets

DUE TODAY!!!COMPOSITION NOTEBOOK CHECK (Journal Entries will begin next week)

MONDAY AUGUST 8, 2016

All Periods will meet in Lab 2

Admit Ticket

W h a t i s t h e d i f f e re n c e between Speed and Velocity? Wr i t e yo u r a n s w e r i n a complete sentence.

Exit Ticket

Based on today’s lesson, fill in the blanks with the correct answer. _____________________________ refers to increasing or decreasing speed and changing direction.

_____________________________ is an international unit for measuring distance.

_____________________________ is the speed and direction of an object.

Motion

The Need for Speed

What is motion?

• You are probably thinking that motion is when something is moving…

• Unfortunately, that definition won’t do us much good.

• How do we know something is moving? • How do we measure it? • How do we tell fast motion from slow

motion?

Well…• An object is in motion when its distance from

another object is changing.

• We can tell something is moving when we can measure it!

• Motion is described relative to something else. We call this place or object used for comparisons to determine if something is in motion a reference point. – For example, even though you are in your seat, you

are moving 30k/s relative to the sun!

How do we measure motion?

• We measure motion based on how fast it is occurring, or better put, the rate at which it occurs.

•Rate tells us the amount of something that occurs or changes in one unit of time.

• You are probably more familiar with this concept when referring to speed.

The Need for Speed!

• Speed is one type of rate.

• The speed of an object is the distance the object travels per unit of time.

• Lets think of driving. Most streets in Phoenix are 45 miles per hour. So, if I drive the rate of 45 miles per hour, then I will travel 45 miles in one hour!

How do I calculate speed?

• Speed=Distance Time

S=D TOR

A cheetah can maintain a constant speed of 25m/s. At this rate, how far will it travel in 10 s?

• Remember the steps of problem solving!

• 1. Write the equation & rearrange. S=D/T or D=ST 2. Write the knowns S=25m/s D= ? T= 10s

3. Convert – We don’t need to

4. Plug! D=(25m/s) x (10s)

5. Chug! D=(25m/s) x (10s) =250m

6. Box Answer!

Velocity

• Society uses the terms “speed” and “velocity” interchangeably.

• But…they are wrong.

•Velocity is speed with a given direction

• So, speed is going 30m/h

• Velocity is going North 30m/h

“We’re not in Kansas anymore…

• If we lived in Kansas during Tornado season, it really wouldn’t do us much good to know the speed of a storm traveling with a tornado brewing inside it.

• But… • It would be very beneficial to know the

speed of a tornado, and the direction, especially if it is headed toward our house.

The Rubber Hits the Road…

• Speed is distance over time

• Example: 65 m/h

• Velocity is speed and direction

• Example: 65 m/h South

Motion

Acceleration

Acceleration

• Consider a car stopped at a stoplight. As the light turns green, the driver presses the gas pedal and gradually increases speed, or accelerates.

• Acceleration is the rate at which velocity changes.

• Remember, velocity is speed and direction.

Velocity change

• Velocity can either increase or decrease

• The direction can also change

• Acceleration involves a change in either of these components.

• Acceleration refers to increasing or decreasing speed and changing direction.

Increasing Speed

• When an object increases speed, it experiences acceleration.

• When a football is thrown, it accelerates.

• When a pitcher throws a ball, it accelerates.

• When a horse begins to run, it accelerates.

Decreasing Speed

• Objects that speed up, eventually slow down.

• A ball that is thrown eventually rolls to a stop.

• A car slows down as the driver steps on the brake.

• A runner finishing a race, eventually stops.

Changing Direction

• Acceleration is change in speed or direction.

• A car accelerates as it makes a turn.

• A Ferris Wheel at the fair is accelerating (direction is always changing)

• The Earth rotating around the sun.

Calculating Acceleration

• To determine the acceleration of an object, you must calculate the change in velocity during each unit of time.

Final Velocity - Initial Velocity Acceleration= Time

How else can we simplify the equation?

• We can summarize the acceleration equation by the following:

Vf - Vi A= t

Units

• If velocity is measured meters/second

• And time is measured in seconds,

• Then, acceleration is measured in meters per second per second.

• Acceleration units are m/s2

An Example:

• A roller coaster car rapidly picks up speed as it rolls down a slope. As it starts down the slope, its speed is 4 m/s. But 3 seconds later, at the bottom of the slope, its speed is 22m/s. What is its average acceleration?

• Relax! This is easy, just follow the steps for solving word problems!

Just follow the steps!

Step 1: Write the equation Vf – Vi A= t

A roller coaster car rapidly picks up speed as it rolls down a slope. As it starts down the slope, its speed is 4 m/s. But 3 seconds later, at the bottom of the slope, its speed is 22m/s. What is its average acceleration?

Step 2: Write the knowns:

A=?

t= 3 s

Vf=22 m/s

Vi=4 m/s

Step 3: Convert

-Not needed

Step 4: Plug!

22 m/s – 4 m/s

A=

3s

Step 5: Chug! 18m/s

A= = 6 m/s2

3s

Step 6: Box Answer!

SpeedMeasuring motion

Measuring Distance

○ Meter – international unit for measuring distance.

= 50 m1 mm

Calculating Speed

○ Speed (S) = distance traveled (d) / the amount of time it took (t).

S = d/t

Units for speed

○ Depends, but will always be a distance unit / a time unit

● Ex. Cars: mi./h ● Jets: km/h ● Snails: cm/s ● Falling objects: m/s

Calculating speed

○ If I travel 100 kilometer in one hour then I have a speed of…

○ 100 km/h

○ If I travel 1 meter in 1 second then I have a speed of….

○ 1 m/s

S = d/t

Question

○ I travelled 25 km in 10 minutes. What is my speed? ● A) 25000 km/min ● B) 250 km/min ● C) .025 km/min ● D) 2.5 km/min

Average speed

○ Speed is usually NOT CONSTANT ● Ex. Cars stop and go regularly ● Runners go slower uphill than downhill

○ Average speed = total distance traveled/total time it took.

Calculating Average Speed

○ It took me 1 hour to go 40 km on the highway. Then it took me 2 more hours to go 20 km using the streets.

○ Total Distance: ● 40 km + 20 km = 60 km

○ Total Time: ● 1 h + 2 h = 3 hr

○ Avg. Speed: ● total d/total t = 60 km/3 h = 20 km/h

Question○ I ran 1000 m in 3 minutes. Then ran

another 1000 m uphill in 7 minutes. What is my average speed? ● A) 100 m/min ● B) 2000 m/min ● C) 10 m/min ● D) 200 m/min ● E) 20 m/min

Total Dist. = 1000 m + 1000 m = 2000 m

Total Time = 3 min + 7 min = 10 min

Avg speed = total dist/total time =

2000m/10 min = 200 m/min = D

Graphing Speed: Distance vs. Time Graphs

Distance(Km)

0

350

700

1050

1400

Time(hr)

1 2 3 4 5 6 7

Phoenix

Denver

Graphing Speed: Distance vs. Time Graphs

Distance(km)

0

350

700

1050

1400

Time(hr)

1 2 3 4 5 6 7

Run

Graphing Speed: Distance vs. Time Graphs

Distance(km)

0

350

700

1050

1400

Time(hr)

1 2 3 4 5 6 7

Run=?3 h

600 km

Graphing Speed: Distance vs. Time Graphs

Distance(km)

0

350

700

1050

1400

Time(hr)

1 2 3 4 5 6 7

Run=?3 minutes

600 m

Different SlopesD

ista

nce

(km

)

0

2

4

5

7

Time (hr)1 2 3 4 5 6 7

Run = 1 hr

Run = 1 hr

Run = 1 hr

Rise = 0 km

Rise = 2 km

Rise = 1 km

Slope = Rise/Run = 1 km/1 hr = 1 km/hr

Slope = Rise/Run = 0 km/1 hr = 0 km/hr

Slope = Rise/Run = 2 km/1 hr = 2 km/hr

Question

○ Below is a distance vs. time graph of my position during a race. What was my AVERAGE speed for the entire race?

Dis

tanc

e (k

m)

0

3

6

9

12

Time (hr)0 1 2 3 4 5 6

Average Speed = Total distance/Total time = 12 km/6 hr = 2 km/hr

Run = 6 hr

Rise = 12 km

Question

○ What does the slope of a distance vs. time graph show you about the motion of an object?

○ It tells you the SPEED

Question

○ Below is a distance vs. time graph for 3 runners. Who is the fastest?

Dis

tanc

e (m

i.)

0

2

3

5

6

Time (h)0 1 2 3 4 5 6

Bob JaneLeroy

Leroy is the fastest. He completed the race in 3 hours

Acceleration

○ Acceleration = speeding up

○ Acceleration – the rate at which velocity changes ● Can be an:

○ Increase in speed ○ Decrease in speed ○ Change in direction

Types of acceleration

○ Increasing speed ● Example: Car speeds up at green light

○ Decreasing speed ● Example: Car slows down at stop light

○ Changing Direction ● Example: Car takes turn (can be at

constant speed)

screeeeech

Velocity

○ Velocity – the SPEED and DIRECTION of an object.

● Example: ○ An airplane moving North at 500 mph ○ A missile moving towards you at 200 m/s

Question

○ What is the difference between speed and velocity?

○ Speed is just distance/time. Velocity includes direction as well.

Question

○ How can a car be accelerating if its speed is a constant 65 km/h?

○ If it is changing directions it is accelerating

Calculating Acceleration

○ If an object is moving in a straight line

○ Units of acceleration: ● m/s2

Calculating Acceleration

0 s 1 s 2 s 3 s 4 s

0 m/s 4 m/s 8 m/s 12 m/s 16 m/s

Question

○ A skydiver accelerates from 20 m/s to 40 m/s in 2 seconds. What is the skydiver’s average acceleration?

Graphing Acceleration

○ Can use 2 kinds of graphs ● Speed vs. time ● Distance vs. time

Graphing Acceleration:Speed vs. Time Graphs

Spee

d (m

/s)

0

3

6

9

12

Time (s)0 1 2 3 4 5 6

1)Speed is increasing with time = accelerating 2)Line is straight = acceleration is constant

Graphing Acceleration:Speed vs. Time Graphs

Spee

d (m

/s)

0

3

6

9

12

Time (s)0 1 2 3 4 5 6

1)In Speed vs. Time graphs: Acceleration = Rise/Run

= 4 m/s ÷ 2 s = 2 m/s2

Run = 2 s

Rise = 4 m/s

Graphing Acceleration:Distance vs. Time Graphs

Dis

tanc

e (m

)

0

10

20

30

40

Time (s)0 1 2 3 4 5

1)On Distance vs. Time graphs a curved line means the object is accelerating.

2)Curved line also means your speed is increasing. Remember slope = speed.

QuestionSp

eed

(m/s

)

0

3

6

9

12

Time (s)0 1 2 3 4 5 6

Above is a graph showing the speed of a car over time. 1) How is the speed of the car changing (speeding up, Slowing down, or staying the same)? 2) What is this car’s acceleration?

1) The car is slowing down 2) Acceleration = rise/run = -6m/s ÷3s = -2 m/s2

Run = 3 s

Rise = -6 m/s

Question:D

ista

nce

(m)

0

10

20

30

40

Time (s)0 1 2 3 4 5

1)Which line represents an object that is accelerating?

The black and red lines represent a objects that are accelerating. Black is going a greater distance each second, so it must be speeding up. Red is going less each second, so must be slowing down

Remember: in distance vs. time graphs: curved line = accelerating, flat line = constant speed

Question: Hard oneSp

eed

(m/s

)

0

3

6

9

12

Time (s)0 1 2 3 4 5 6

Above is a graph showing the speed of a car over time. 1)What would a distance vs. time graph for this look like?

Dis

tanc

e (m

)

0

13

25

38

50

Time (s)0 1 2 3 4 5 6

CONSTANT VELOCITY LAB:

BUGGY CARS

Team Positions Time Keeper(s)

Data Recorder

Tape Marker

Measurer

Car Operator

Purpose Examine the motion of the buggy

Measure the position of the buggy with respect to time

Create a position vs. time graph for the buggy

Develop a mathematical model for the motion of the buggy

Materials Dune buggy

Meter Stick

Stop Watch

Tape (marking device)

Homework Due

“CALCULATING SPEED” WORKSHEET DUE MONDAY, AUGUST 8, 2016

MONDAY AUGUST 8, 2016

All Periods will meet in Lab 2