Describing Motion

Motion Starter #2

• Work as a group of 4 at your table and “play” with the battery operated toy cars. Use any additional materials you might need – meter stick, tape, timer, wood blocks etc.

PLEASE USE THEM ON THE FLOOR NOT ON THE TABLES!

• Describe the motion of these toys. Write your description on a sticky note and put it on the board when finished.

Motion Starter

•What words did you use to describe the motion? Share the sticky notes.

Describing Motion• Describe the motion of these wind-up

toys.– How far does it move? – How fast does it move? – Does it move at a steady rate, speed up,

or slow down?.– What direction does it move?

• These all describe MOTION.

Measuring Motion• As a table group come up with

definitions for OR drawings to show

Distance vs. Displacement • Be sure to clearly show the difference

between the two!

• Write your definitions/draw pictures on 2 different sticky notes and put them on the board.

Measuring MotionDISTANCE DISPLACEMENT

Measuring Motion• Distance – total change in position

• Displacement –

change in

position IN A

STRAIGHT LINE

(from point A to point B)

A

B

Motion song

What is Motion Video

Is your desk in motion?

TRY THIS! Is your desk in motion?

• We need a reference point…

Define Reference Point: nonmoving point from which motion is measured

TRY THIS! Is your desk in motion?

• From the reference point of your seat is you desk in motion?

TRY THIS! Is your desk in motion?

• From the reference point of your seat is you desk in motion?

NO!

TRY THIS! Is your desk in motion?

• From the reference point of space, is your desk in motion?

TRY THIS! Is your desk in motion?

• From the reference point of space, is your desk in motion?

YES!

Reference Point• Define Motion:

Reference point

Motion

Reference Point• Define Motion

A change in position in relation to a reference point.

Reference point

Motion

Frame of Reference

VIDEO 2

1) DESCRIBE THE MOTION OF THE BALL FROM THE POINT OF VIEW OF THE AUDIENCE.

2) DESCRIBE THE MOTION OF THE BALL FROM THE POINT OF VIEW OF THE CART FROM WHICH IT IS SHOT.

Frame of Reference

VIDEO 1

11

Frame of Reference

VIDEO 3

11

Frame of Reference

VIDEO 4 111) DESRCRIBE THE MOTION OF THE ORANGE FROM THE POINT

OF VIEW OF A PERSON STANDING ON THE TRAIN

1) DESCRIBE THE MOTION OF THE ORANGE FROM THE POINT OF VIEW OF SOMEONE WATCHING THE TRAIN PASS BY THEM ON THE STREET.

MEASURING DISTANCE & DISPLACEMENTS

1. Read pages 329-330 to learn about:a. Measuring distance

b. Measuring displacements

c. Combining displacements

2. Answer the Exit Ticket Questions when you are ready.

DESCRIBING MOTION EXIT TICKET1. What is a frame of reference and how is it used to

measure motion?

2. How are distance and displacement similar and different?

3. How are displacements combined?

4. A girl who is watching a plane fly tells her friend that the plane isn’t moving at all. Describe a frame of reference in which the girl’s description would be true.

5. Would your directions to a friend traveling from one city to another include displacements or distances? Explain.

DESCRIBING MOTION EXIT TICKETANSWERS

1. Frame of reference is a set of objects that are not moving with respect to one another. Motion can only be describe in comparison to a frame of reference.

2. Distance is the length of an object’s actual path from a starting point to an ending point. Displacement is the length of a straight line from the starting point to the ending point.

3. Displacements are combined using vector addition.

DESCRIBING MOTION EXIT TICKETANSWERS

4. If the plane is far away and flying directly toward or away form the girl, the plane would appear not to be moving. Also, the plane would not be moving int eh frame of reference of the people on the plane.

Quick Lab• Do the Lab on page 330 in your

textbook

• Use the graph paper on the other side of your Motion Exit Ticket.

• Exchange your paper with a partner when you’re finished.

• Determine the distance and displacement of their path

• ASSESS: Draw a shape with a distance of 10 and a displacement of 0

Speed starter

Complete the “Skate Park” challenge

Speed

• Speed – the rate at which an object changes its position

• What is your speed if you cover 240 miles in 4 hours?

• Never Fear! Equation person is here!

• S = d/t

• What is your speed if you cover 240 miles in 4 hours?

time

distancespeed

• S = d/t

• What is your speed if you cover 240 miles

in 4 hours?

• S = 240/4 = 60 mi/hr!!

time

distancespeed

sd

t

Units in Your Answer• Example units

–TIME: Seconds, Minutes, Hours

–DISTANCE: Miles, Feet, Meters

–SPEED: Miles/Hour, Feet/Second,

Meters/second• Units are CLUES!

Try This!

What is the speed of a car moving 124 miles in 2 hours? (SHOW EQUATION, correct answers, and units!)

• 124 miles = DISTANCE

• 2 hours = TIME

• Solve for SPEED!

ANSWER

• S = d/t

• 124/2 = 62 mi/hr

(mph)

sd

t

MEASURING SPEED• Measure distance in meters,

miles, kilometers

• Measure time in seconds, hours,

• Measure speed in

m/s, mph, m/h, km/h

Now it’s time for a LAB!!

Take a Walk in the Park!

Let’s practice!

time

distancespeed

sd

t

During a trip, you have…

• Average speed your average speed over the whole trip

• Instantaneous speed your speed at any given instant during the trip

You travel from Columbus to Cincinnati (220 miles) in 4 hours.

– What is your speed? – Did you have this speed throughout the

entire trip? – What was your instantaneous speed at a

stop sign?

• Average speed your average speed over the whole trip

• Instantaneous speed your speed at any given instant during the trip

You travel from Columbus to Cincinnati (220 miles) in 4 hours.

– What is your speed? – Did you have this speed throughout the

entire trip? NO! It’s your AVERAGE speed.

– What was your instantaneous speed at a stop sign?

• Average speed your average speed over the whole trip

• Instantaneous speed your speed at any given instant during the trip

You travel from Columbus to Cincinnati (220 miles) in 4 hours.

– What is your speed? – Did you have this speed throughout the

entire trip? NO! It’s your AVERAGE speed.

– What was your instantaneous speed at a stop sign? 0 m/h

• Average speed your average speed over the whole trip

• Instantaneous speed your speed at any given instant during the trip

Back to Equation Person!• S = d/t

• What type of speed are you calculating with this equation? Instantaneous or Average?

Back to Equation Person!• S = d/t

• What type of speed are you calculating with this equation? Instantaneous or Average?

time total

distance totalspeed avg.

What is the car’s AVERAGE speed?

Then let’s practice calculating Average Speed

Speed Formula Song!

A storm is 10 km away and is moving at a speed of 60 km/h. Should you be worried?

A storm is 10 km away and is moving at a speed of 60 km/h. Should you be worried?

It depends on the storm’s direction!

Velocity• Velocity is speed

with a DIRECTION.• Example:

70 mph is a speed

(a scalar qty)

70 mph North is

a velocity

(a vector qty)

Calculating Velocity

Average Velocity = change in position

time

V = position = displacement

time time

This symbol

means

“a change in”

Remember: displacement is the total change in position in a straight line

from point A to point B

What is Earth’s Velocity?

• Earth rotates 25,488 miles counterclockwise in 24 hours. –SHOW EQUATION,

ANSWER, UNITS!http://www.universetoday.com/

26623/how-fast-does-the-earth-rotate/

Wait, the Earth has Velocity?

• Check out these links:• http://www.scientificamerican.com/

article/how-fast-is-the-earth-mov/

• http://www.windows2universe.org/kids_space/vel.html

• http://www.universetoday.com/26623/how-fast-does-the-earth-rotate/

• https://www.youtube.com/watch?v=r4Ts66qcMuc

ANSWER

• V = d/t with direction

• 25,488/24 = 1062 mi/hr Counter-clockwise

• THAT’S FAST!

Let’s Finish the “Walk in the Park” lab

Let’s practice

Speed & Velocity

(homework on 9/4)

Changing Velocity

• Sometimes objects CHANGE velocity as they move.

Example: Roll car down a ramp.

How is its velocity CHANGING?• This is known as ACCELERATION!

Acceleration Demo

Acceleration• Acceleration is a change in VELOCITY due to a

change in direction or speed.– Speed up– Slow down– Change direction

Three Examples of Acceleration

ACCELERATION IS A RATE OF CHANGE in velocity!!

What is the acceleration of the car between 0 seconds and 2

seconds?

Equation Person Returns!

• Your engine shuts off and you slow down from 60 mph to 0 mph in 3 seconds. What is your acceleration?

• What are the units of your acceleration?

t

vva if

a: acceleration

vf: final velocity

vi: initial velocity

t: time

ANSWER

A = 0 – 60

3

-20 mi/hr/sec

a

vf - vi

t

a: acceleration

vf: final velocity

vi: initial velocity

t: time

NEGATIVE Acceleration??

• Positive acceleration

–“speeding up”

• Negative acceleration

–“slowing down”

That makes sense, since we went from 60 0 !!

A = Vf – Vi

T

Vf = 8m/2sec = 4m/sVi = 0 m/sT = 2 sec

Let’s practice!

Then, Time for a LAB!!

Ticker-Tape Machine Lab

Acceleration