Constant Motion

Reference Point

A fixed point from which direction is defined.

The reference point can be anything.

Distance

The length traveled along a trip measured from start to finish.

Example #1

A car drives 4 meters north, 3 meters south then 5 meters north. What’s its total distance driven?

4m + 3m + 5m =

Total distance driven 12m

Direction

Represented by the using :(+) or (-) signsUp or DownRight or LeftForward or BackwardNorth, South , East or West

Position

The location of an object, relative to the reference point.

Displacement

The difference between two positions.

d = dfinal – dinitial

Example #2

A car drives 4 meters north, 3 meters south then 5 meters north. What’s its displacement?

Time Interval

The difference between two clock readings

t = tfinal – tinitial

Average Speed

Total distance traveled divided by the total time elapsed.

v = d / t

Average Velocity

Total displacement divided by the total time elapsed.

v = d / t

Average Acceleration

Average velocity divided by the time.

a = v / t

Example #3

While Ned is traveling along a straight interstate highway, he notices that the kilometer marker reads 260. Ned reaches the 150-kilometer marker 45 minutes later then retraces his path for one hour before arriving at the 225-kilometer marker.

Use the GUESS Method Skills Sheet 

 

Example #3A

How far (distance) did Ned travel?G: dinitial = 260 km

dfinal = 150 kmt = 45 minutes

dinitial = 150 kmdfinal = 225 kmt = 1 hour

Answer: 185 km

U: distance

Example #3B

What’s Ned’s total displacement?G: dinitial = 260 km

dfinal = 150 km

U: displacement

dinitial = 150 kmdfinal = 225 km

ANSWER: 35 km

Example #3C

What’s Ned’s average speed in meters per second?

→ 185 x 103m

U: average speed t = 1 hour 45 minutes

G: d = 185 km → 6300 s

E: v = d/tS: v = (185 x 103 m )/ (6300s)

S: v = 29.365 m/s

Example #3D

What’s Ned’s average velocity in meters per second?G: d = 35 km → 35 x 103 m

U: average velocity

E: v = d/t

S: v = (x 103 m)/ s

S: v = 5.556 m/s

t = 6300 s

Example #4 What is the time required to make a 300 km trip if the average speed

is 29 m/s? Show your answer in base units and correct scientific notation form.

G: d = 300 km → 300 x 103 m

U: t

E: v = d/t

S: t = (x 103 m)/ m/s

S: t = 1.0345 e 4 s

v = 29 m/s

→ t = d/v

Example #5 A dolphin swims 1.85 km/h. How far has the dolphin traveled after

0.60 h? Show your answer in base units and correct scientific notation form.

G: v = 1.85 km/h → 1.85 x 103 m / 3600 s

U: d

E: v = d / t

S: d = (x 10-1 m/s)( s )S: v = 1.11e 3 m

t = 0.6 h → 2160 s

→ tv = d

Example #6 A sailboat moves at a constant speed of 2 m/s. How far does it travel

every ten seconds? Show your answer in base units and correct scientific notation form.

G: v = 2 m/s

U: d

E: v = d/t → d = tv

S: d = ( s)(m/s)

S: d = 20 m

t = 10 s

Example #7 A truck is traveling at a constant velocity of 70 km/h. Convert the velocity to m/s.

G: v = 70 km / h

U: v in (m / s)

E: simple conversion

S: ( 70 x 103 m ) / 3600 s

S: 1.944 e 1 m/s