• Contrast two types of electronic timing equipment • Discuss units of time and significant figures • Relate accuracy and precision to the
Dec 25, 2015
• 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
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.
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
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• 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.”
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)
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
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