• Contrast two types of electronic timing equipment

• Discuss units of time and significant figures

• Relate accuracy and precision to the measures of our lab equipment

Describe the time shown on the $15 stopwatch.

How fast can you start and stop the stopwatch?

Describe the time shown on the $350 timer from CPO.

Channel Setting Instructions for ResponseCard RF

1. Press and release the "GO" or "CH" button.

2. While the light is flashing red and green, enter the 2 digit channel code (i.e. channel 1 = 01, channel 21 = 21).

Channel is 52

3. After the second digit is entered, Press and release the "GO" or "CH" button. The light should flash green to confirm.

4. Press and release the "1/A" button. The light should flash amber to confirm.

How fast can you start and stop the CPO timer?

Which stopwatch is more accurate?

$15 stopwatch $350 CPO timer Other response

0% 0%0%

1. $15 stopwatch

2. $350 CPO timer

3. Other response

Why do you think the two timers have the same level of precision,

two decimal places?

0%0%

Coincidence only For a specific re...

1. Coincidence only

2. For a specific reason

Which of the following registers the time corresponding to the

fastest object being timed?

1.0

67 s

0.9

60 s

0.2

50 s

0.1

79 s

0.1

00 s

0% 0% 0%0%0%

1. 1.067 s

2. 0.960 s

3. 0.250 s

4. 0.179 s

5. 0.100 s

Two runners run a race and their times are separated by 0.01

seconds. Who wins?

Runne

r A w

ith a

tim

e ..

Runne

r B w

ith a

tim

e...

0%0%

1. Runner A with a time of 10.00 s

2. Runner B with a time of 10.01 s

Two runners run a race and their times are separated by 0.01 seconds. Was the stopwatch precise/accurate enough to

determine the winner?

YES

NO

0%0%

1. YES

2. NO

Follow my instructions through the use of the photogate timers.

Which situation displays the time photogate A was blocked?

1 2 3 4

None

of the

se

0% 0% 0%0%0%

1. 2.

3. 4.

1. 1

2. 2

3. 3

4. 4

5. None of these

2.

4.

Which situation displays the time the light at photogate B was blocked?

1 2 3 4

None

of the

se

0% 0% 0%0%0%

1. 2.

3. 4.

1. 1

2. 2

3. 3

4. 4

5. None of these

2.

4.

Which situation displays the time it takes an object to pass between

the two photogates?

1 2 3 4

None

of the

se

0% 0% 0%0%0%

1. 2.

3. 4.

1. 1

2. 2

3. 3

4. 4

5. None of these

2.

4.

When both time lights are off and an object passes through the photogates,

what, if anything, is recorded?

Tim

e at

A

Tim

e at

B

Tim

e fro

m A

to...

All

of the

abo...

Noth

ing

0% 0% 0%0%0%

1. Time at A

2. Time at B

3. Time from A to B

4. All of the above

5. Nothing

Lab Sheet

If I were to perform an experiment in which a car was down a ramp to measure a variable, I would need to recognize what all of the potential variables could be.

• Brainstorm as many variables as you can.

Types

Control OR Experimental

Independent OR Dependent

How many variables did you come up with?

1 2 3 4 5 6 7 8 9

0% 0% 0% 0% 0%0%0%0%0%

1. 1

2. 2

3. 3

4. 4

5. 5

6. 6

7. 7

8. 8

9. 9

Lab

What are the variables in this experiment?1.Distance between A & B2.Position of A & B3.Weight4.Starting point5.Friction6.Start technique7.Ramp angle

Types

Control OR

Experimental

Independent OR

Dependent

Motion

• Aristotle (4th Century BC) used logic incorrectly

1. Motion requires force

2. Heavier objects fall faster

3. Natural motion (up and down) vs unnatural motion (push and pull)

1500’s Galileo

• Experiments are better at testing knowledge than logic

Galileo

1. Objects of different weights fall to the ground in the same time

Galileo• Force is needed to start movement but none after it

starts if friction is not present

?

Ball rolls farther as angle of inclination on the right is reduced

Galileo • Speed Formula

• S=distance

time

Say the following in fewer words.

“She moves in a constant speed in a constant direction.”

“She moves at constant velocity.”

Formative assessments

• Teacher’s manual margin learning checks with yellow backgrounds

Differentiate speed and velocity: Speed is distance divided by time whereas velocity is displacement

divided by time?

Corre

ct

Inco

rrec

t

0%0%

1. Correct

2. Incorrect

Differentiate speed and velocity: Velocity includes direction and

speed does not.

Corre

ct

Inco

rrec

t

0%0%

1. Correct

2. Incorrect

Differentiate speed and velocity: Speed is measured in m/s and velocity is measured in km/h.

Corre

ct

Inco

rrec

t

0%0%

1. Correct

2. Incorrect

Differentiate speed and velocity: the speed of an object is always

constant. The velocity of an object can change.

Corre

ct

Inco

rrec

t

0%0%

1. Correct

2. Incorrect

Lab pink sheet

What are the variables in this experiment?1.Distance between A & B2.Position of A & B3.Weight4.Starting point5.Friction6.Start technique7.Ramp angle

Types

Control OR

Experimental

Independent OR

Dependent

Lab B-4

• Average Speed– Distance / Time

A B distance (cm)

A B time (sec)

Lab B-4• Predicting Speed (instantaneous)at various Points on the Ramp

Instantaneous Speed

ORWing of Car

Lab B-4• Determine the relationship

between Slope and Speed

Average Speed

ANDDistance & time between Photogates

Lab B-4 Distance vs Time Graph

Distance

A-B (cm)

Time A-B (sec.)

• Steeper the Slope = faster the speed

Speed increases down the ramp

Galileo developed the concept of acceleration

A = v

t

In an automobile, what produces acceleration or deceleration in a car?

Accelerator, brakes, steering wheel…. a hill?

What limits (resists) acceleration?

MASS

a = 1 / mass

(inversely proportional)

FRICTIONAL FORCE

AIR DRAG

A plane taking off…

Is a

n exa

mple

of a

cce.

..

Is n

ot an e

xam

ple o

f...

0%0%

1. Is an example of acceleration

2. Is not an example of acceleration

A person walking 1.5 m/s along a winding path…

Is a

n exa

mple

...

Is n

ot an e

xam

...

0%0%

1. Is an example of acceleration

2. Is not an example of acceleration

A car driving 88 km/h on a flat, straight stretch of highway….

Is a

n exa

mple

of a

cce.

..

Is n

ot an e

xam

ple o

f...

0%0%

1. Is an example of acceleration

2. Is not an example of acceleration

A bicyclist stopping at a stop sign.

Is a

n exa

mple

of a

cce.

..

Is n

ot an e

xam

ple o

f...

0%0%

1. Is an example of acceleration

2. Is not an example of acceleration

Lab B-5• Acceleration

Change in speed (cm/sec) = cm/sec2

change in time (sec) cm/s per s or cm/s

s

Time A-B (sec.)

Speed

A-B

(cm/sec)

Constant Acceleration

(due to gravity)WHY?

Lab B-5• Acceleration

Change in speed (cm/sec) = cm/sec2

change in time (sec)

Time A-B (sec.)

Speed

A-B

(cm/sec)

Constant Acceleration

(due to gravity)

OVERVIEW

A

B

Instantaneous Speeds (at A and B)

Average Speed

(between A&B)

UNITSDistanceDisplacement

cmcm downhill or E

TimeChange in TimeTime Interval

Seconds

Speed cm/sec

AccelerationSpeed increase over time

cm/sec2

cm/sec per sec

1. Which of these forces opposes the motion of the car?

fric

tion

wei

ght

mas

s

gra

vity

0% 0%0%0%

1. friction

2. weight

3. mass

4. gravity

1. Which of these forces helps the motion of the car?

fric

tion

wei

ght

mas

s

gra

vity

0% 0%0%0%

1. friction

2. weight

3. mass

4. gravity

Equation F=ma Units N=kg m/s2

• Friction is a force opposing motion (N or kg m/s2)

• Weight is force that is the mass x the acceleration due to gravity (F=ma or w=mg)

(N or kg m/s2) Not the best choice because changing the mass does not change

the acceleration.

• Mass is not a force; it is the amount of matter in an object (kg)

• Gravity is the force creating the acceleration between two objects

The steeper the ramp, the _____ the speed.

gre

ater

less

Ther

e is

no im

pact

0% 0%0%

1. greater

2. less

3. There is no impact

The steeper the ramp, the _____ the acceleration.

gre

ater

less

Ther

e is

no im

...

0% 0%0%

1. greater

2. less

3. There is no impact

What type of relationship is shown in graph

dire

ct

inve

rse

No re

latio

nship

0% 0%0%

1. direct

2. inverse

3. No relationship

What type of relationship is shown in graph

dire

ct

inve

rse

No re

latio

nship

0% 0%0%

1. direct

2. inverse

3. No relationship

What type of relationship is shown in graph

dire

ct

inve

rse

No re

latio

nship

0% 0%0%

1. direct

2. inverse

3. No relationship

What type of relationship is shown in graph

dire

ct

inve

rse

No re

latio

nship

0% 0%0%

1. direct

2. inverse

3. No relationship

Which correctly describes the mathematical relationship of Newton’s

second law?

m=F

/a

a=F/

m

F=m

a

All

of thes

e ar

e co

rrec

t

None

of the

se a

re c

or...

0% 0% 0%0%0%

1. m=F/a

2. a=F/m

3. F=ma

4. All of these are correct

5. None of these are correct

In the lab, which of the following calculation showed a direct mathematical relationship for

acceleration with positive slope for the calculation of Newton’s second law?

a= F

/ m

a= m

/ F

a= m

- F

a= m

x F

None

of the

se ..

.

0% 0% 0%0%0%

1. a= F / m

2. a= m / F

3. a= m - F

4. a= m x F

5. None of these are correct

A student is pedaling a bike by applying a net force of 250 N. The mass of the bike and rider is

50 kg. Assuming no friction, what is the acceleration of the bike and rider?

50

kg

12,

500

kg

.2 k

g

5 k

g

None

of the

se a

re c

or...

0% 0% 0%0%0%

1. 50 kg

2. 12,500 kg

3. .2 kg

4. 5 kg

5. None of these are correct

More graphical analysis and equations

Sketch the graph as you think it should be

Galileo vs. Newton

• Concerned with “how things work?”

Concerned with “why things work?” (CH. 10)

When a net force acts on an object, the motion of the object does not

change.

Corre

ct

Inco

rrec

t

0%0%

1. Correct

2. Incorrect

When a net force acts on an object, the speed of the object always

increases.

Corre

ct

Inco

rrec

t

0%0%

1. Correct

2. Incorrect

When a net force acts on an object, the object’s direction of motion will

always change.

Corre

ct

Inco

rrec

t

0%0%

1. Correct

2. Incorrect

When a net force acts on an object, the object accelerates in the direction

of the net force.

Corre

ct

Inco

rrec

t

0%0%

1. Correct

2. Incorrect

#7

A B C D

0% 0%0%0%

1. A

2. B

3. C

4. D

#8

A B C D

0% 0%0%0%

1. A

2. B

3. C

4. D

#9

A B C D

0% 0%0%0%

1. A

2. B

3. C

4. D

#10

A B C D

0% 0%0%0%

1. A

2. B

3. C

4. D

#11

A B C D

0% 0%0%0%

1. A

2. B

3. C

4. D

#12

A B C D

0% 0%0%0%

1. A

2. B

3. C

4. D

#13

A B C D

0% 0%0%0%

1. A

2. B

3. C

4. D

#14

A B C D

0% 0%0%0%

1. A

2. B

3. C

4. D