day 1 unit 1 motion graphs
TRANSCRIPT
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UNIT 1
Motion Graphs
Lyzinski Physics
x
t
Day 1
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- MechanicsKINEMATICS
DYNAMICS- Electricity
- Magnetism
- Optics
- Waves
PHYSICSA “description” of motion
A study of what “causes”
motion
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Day #1
* Distance
* Speed
* Unit Conversions
* Scalars
* d-t graphs
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Definition
Distance (d) – the length of the path
followed by an object.
* If an object’s path is straight, the distance is the length of
the straight line between start and finish.
** If an object’s path is NOT straight, the distance is the
length of the path if you were to “straighten it out” and
measure it the way you would measure the length of a
curved shoelace.
start
finish
start
finish
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Using the number line above, what would be the distance
travelled if an object travelled from …..
- A to B
- A to C
- A to C and then back to A
- C to B, passing through A
B C
-3 -2 -1 0 1
A
meters
1m
4m
4m + 4m = 8m
4m + 1m = 5m
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5 yd12 yd
A
B
C
Sally and Timmy are at point A.
Sally walks directly to point C (taking the shortest path).
Timmy also takes a “shortest path”, but has to stop at point
B for lunch first.
How much further has Timmy walked when he arrives?
4 yd
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Definition
Average Speed (s) – the distance
travelled during a time interval divided
by the elapsed time.
s = d/Dt
(or s=d/t) we often abbreviate
”Dt” as “t”
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Larry walks from point B to point C, and then goes directly
to point A. If he walks at an average speed of 6 mph, how
long does the trip take him?
B C
-3 -2 -1 0 1
A
miles
d = 3mi + 4mi = 7mi
s = 6 mi/h
s = d/t t = d/s = (7mi)/(6mi/h)=1.17h
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Larry runs from point A to point B in 5 minutes and then
proceeds to jog directly to point C, taking his time in 30
additional minutes. Find…
B C
-3 -2 -1 0 1
A
km
a) Larry’s average speed during the first portion of the trip.
b) The average speed during the second portion of the trip.
c) Larry’s average speed for the entire trip.
s = d/t = (1km)/(5min) = 0.2 km/min = 12 km/h
s = d/t = (3km)/(30min) = 0.1 km/min = 6 km/h
s = d/t = (4km)/(35min) = 0.114 km/min = 6.86 km/h
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Unit Conversions
• Convert 5 km/h to m/s.
• Convert 60 ft/s to mi/h.
• Convert 30 mi/h to m/min!!!!
5km
1h
1000m
1km
1h
3600sec
1.39
m
s
60 ft
1s
1mi
5280 ft
3600sec
1h
40.91
mi
h
30mi
1h
1600m
1mi
1h
60min
800
m
min
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Definition
Scalar – a quantity that has a magnitude
only, no direction.
* YES, scalars can have units.
** What scalars have we learned about thus far?
___________ ____________ ___________distance speed time
I thought time could
march backward?
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d-t graphsConstant speed
Speeding UP
Constant Speed (faster!)
Slowing Down
At rest
t (sec)
d (m)
B
C
E
A
D
F
10 15 20 27 36
120
100
50
30
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Speed on a d-t graph can be found by taking the _______________.SLOPE
sAB = rise/run = (30-0m) / (10-0s) = 3 m/s
sCD = rise/run = (100-50m) / (20-15s) = 10 m/s
t (sec)
d (m)
B
C
E
A
D
F
10 15 20 27 36
120
100
50
30
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Open to in your GREEN packet
520 – 170yd = 350 yd (approximately)
1) On the d-t graph, find the distance travelled from 4 to 16 seconds. ______
1
d-t graphs
CANNOT
have sharp
points
NOTHING CAN STOP
INSTANTANEOUSLY!!
minutes
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HOMEWORK
Check out your Unit 1 Schedule … Day #1
We will “try” to follow it night by night.