Principles of Physics

 motion along a straight line path, motion in one dimension  Which way are you headed?

 How far did you go?

 How fast are you going?

 Is your speed changing?

Direction

 In order to get anywhere you need to know what direction you are headed.

   Up, Down, Left , Right Direction can also be negative or positive for math purposes  North, South, West , East Negative: South, West, Down, Left  Positive: North, East, Up, Right

Almost all quantities have units - examples: meters, seconds, kilograms - Without units numbers would be meaningless Vector – Quantities that include a direction  Vectors can be drawn  They are represented by arrows Example: 12 m south Scalar – Quantities that do not include direction Example: 4 seconds

How far did you go?

Path length (p): total length of path taken - measured in meters(m) - scalar quantity (does not include direction) 2 m 6 m 1 m p = 8 m + 6 m + 2 m + 1 m p = 17 m 8 m

How far did you go?

Displacement (d): change in position, shortest path between start and finish - vector (amount and direction) 2 m 1 m 6 m 8 m

6 m Path Length = 9 m 3 m 6 m Path Length = 9 m 3 m Displacement = 9 m right Displacement = 3 m left 3 m Path Length = 9 m 6 m Displacement = ?

c a

2 

b

2 

c

2     2  6 .

71

m



c

2

northeast

 To determine displacement draw a diagram of the path taken  Example: 8 m east, then 6m north, then 2 m east, then 1 m south 2 m 6 m 1 m 8 m  Simplify the diagram to a right triangle 1 m 6 m 8 m 2 m  Use Pythagorean Theorem to determine the displacement 10 m 5 m

c a

2 

b

2 

c

2  10

m

   2  11 .

2

m



c

2

northeast

Jan walks 4 meters north then turns to walk 4 meters east and finally turns to walk another 8 meters north. Determine Jan’s displacement.

4 m 4 m 8m d 8m 4 m

c a

2 

b

2 

c

2



12

m

  

2  12 .

65

m



c

2

northeast

4 m

Units for path length or displacement: Standard Unit: meter   Anything else must be converted 1 meter = 100 centimeters = .001 kilometer 1 kilometer = 1000 meters   1 meter = 3.28 feet 1 kilometer = 0.6214 miles

Smaller unit to larger unit: divide   centimeters to meters: divide by 100 millimeters to meters: divide by 1000 Larger unit to smaller unit: multiply  kilometers to meters: multiply by 1000

1.

Smaller unit to larger unit: divide Change 40 centimeters to meters 40

cm

100

cm

/

m

 0 .

4

m

2.

Larger unit to smaller unit: multiply Change 6.8 kilometers to meters 6 .

6

km

( 1000

m

/

km

)  6 , 600

m