UNIT 1

Motion Graphs

Lyzinski Physics

x

t

Day 1

- MechanicsKINEMATICS

DYNAMICS- Electricity

- Magnetism

- Optics

- Waves

PHYSICSA “description” of motion

A study of what “causes”

motion

Day #1

* Distance

* Speed

* Unit Conversions

* Scalars

* d-t graphs

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

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

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

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”

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

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

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

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?

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

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

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

HOMEWORK

Check out your Unit 1 Schedule … Day #1

We will “try” to follow it night by night.