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Motion is when an

object changes

position.

Speed (s) is how fast /

slow it changes position.

To calculate speed, we need

1. Distance (how far it went)

2. Time (how long it took)

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Calculating Speed

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HOW

FASTAM I?

Walking person

1.4 m/s

(3.1 mph)

Cruising jet

257 m/s

(575 mph)

Speeding race car

96 m/s

(215 mph)

Flying eagle51 m/s

(114 mph)

Galloping horse

19 m/s

(42 mph)

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To Solve Problems,

use the blocks !!!

INFO ANSWER

with

units!

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Speed Calculation ExamplesFlorence Griffith Joyner set a world record by

running 220 m in 21.34 s. What was heraverage speed?

INFO

d = 220m

t = 21.34s

s = ?

ANSWER

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Speed Calculation ExamplesThe worlds fastest passenger elevator operates

at an average speed of 10 m/s. If the 60th floor is219 m above the first floor, how long does it takethe elevator to go from the 1st to the 60th floor?

INFOd = 219m

t = ?

s = 10m/s

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Distance-Time GraphsAllows us to see the motion of an object.

x-axis:

time (s)

y-axis:

distance

(m)

A straight line =

constant speed.

Slope = change in distance = avg. speed

change in time

Flat slope (horizontal) = at rest.

Steeper slope = faster speed.

s = +

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Graphing Speed Example

TIME DISTANCE

0 min 0 m

10 min 800 m

20 min 1600 m

30 min 2400 m

TIME DISTANCE

0 min 0 m

10 min 400 m

20 min 400 m

30 min 1200 m

Swimmer 1 Swimmer 2

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Speed of Two Swimmers

0 5 10 15 20 25 30

Time (minutes)

2400

22002000

1800

1600

1400

1200

1000

800

600

400

200

0

D

i

s

ta

n

c

e

(m)

What is the total distance

the 1st swimmer swam?

The second swimmer?2400 m

1200 m

What is the avg. speed of

the 1st swimmer?

The second swimmer?

s = d = 2400 m = 80 m/min

t 30 min

s = d = 1200 m = 40 m/min

t 30 min

Compare the avg. speedof the 2ndswimmers 1st

10 min to her last 10 min.1st = 400/10 = 40 m/min

Last = 800/10 = 80 m/min

Her s eed doubled!

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Speed or Velocity?

Velocity is simplyspeed with a direction!

An escaped ostrich heading

toward our campus at 16.2 m/s.

A kitten running up

a tree at 6.5 m/s.

A car heading west on I-10 at 50 mph.

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Momentum

The product of an objectsmass and its velocity.

momentum = mass x velocity

p = mv

UNITS:

m = kg

v = m/s

p = kg m/s

small mass

small velocity

small momentum

large mass

large velocitylarge momentum

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Calculate the momentum of a

6.00 kg bowling ball moving at10.0 m/s down the alley.

INFO

m = 6.00 kg

v = 10.0 m/sdown the alley

p = ?

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ACCELERATION

How fast the velocity is changing!

+ acceleration = speeding up

- acceleration = slowing down

UNITS: a = m/s = m/s2

s

acceleration = final velocityinitial velocity

time

a = VFVI = Vt t

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Velocity-Time GraphAllows us to see the change in the

velocity of an object.

x-axis:

time (s)

y-axis:

velocity

(m/s)

A straight line =

constant

acceleration.

Slope =

acceleration

flat slope (horizontal) = constant velocity

+ slope = speeding up (+ acceleration)

- slope = slowing down (- acceleration)

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As a roller coaster starts down a

hill, its speed is 10m/s. Threeseconds later, its speed is 32 m/s

at the bottom of the hill. What is

the roller coasters acceleration?

INFO

VI = 10 m/s

VF = 32 m/st = 3 s

a = VFVI / t

a = (32 m/s - 10 m/s) / 3 s7.3 m/s2downward

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CH 8 SEC 1 & 2 REVIEW Know the units for distance, time, mass,

speed, velocity, momentum, acceleration.

Be able to calculate

- speed/velocity

- momentum

- acceleration

from a word problem.

Be able to interpret

- speed

- acceleration

graphs.

(**KEEP IN MIND: You will be given all formulas in the

format they will appear on the

TAKS formula sheet.**)

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OBJECT TRIAL

1

TRIAL

2

TRIAL

3

AVERAGE

TIME (s)

SPEED

(cm/s)

v=d/t

MASS

(g)

MOMENTUM

(gm/s)

p=mv

Bouncy

Ball

Racquet /

Sponge

Ball

Golf/Ping

PongBall

Car

DATA TABLE

P L b Q ti

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Pre-Lab Questions1. Rank the following objects from 1-4. Your number

1 should be the object that you think will have the

fastest speed/velocity down the ramp.

Bouncy Ball, Racquet / Sponge Ball,

Golf / Ping-Pong Ball, Car

2. Explain why you have ranked the objects in the

order.

3. What are units we usually use to measure speed?

4. Since this is a science class, and we measure in

metric units, what are units that we can measure

speed in?

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Conclusions

1. Why is finding an average of three trialsmore accurate than just one trial?

2. Which object had the fastest speed, whichhad the slowest?

3. Did your results surprise you? Explain whyor why not.