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• Speed = Distance / Time

• Speed = • ∆ (“delta”) means “change in…”• division sign means “per…”

• Units: miles per hour (mph) meters per second (m/s) kilometers per hour (km/hr)

•5 meters in 1 second: • 5 m/sec

• 10 meters in 2 seconds:• 5 m/sec

• 20 meters in 10 seconds:• 2 m/sec

Biking Speeds:

Velocity: Speed with direction

• Biking at 2 m/sec to the north

• Flying at 120 mph to the SW

Velocity: Speed with direction

• An airplane travels 250 km due north in 1/2 hour.

• Speed? • 500 km/hr

• Velocity? • 500 km/hr north

Vocabulary: Vector vs. Scalar

• Vector: • Has a size (magnitude) AND a

direction• Example – Velocity

• Scalar:• Has a size (magnitude)• Example - Speed

• Speed = =

• Velocity = =

Velocity: Slope of position vs. time graph

=

= = = 10 m/s

• Speedometer: Shows speed at this instant => Instantaneous speed

• Calculate: => Average speed

Instantaneous vs. Average

Drive to Seattle

• Instantaneous speeds:• 31 mph on Cemetery Road• 18 mph slowing down for a traffic

light• 57 mph on I-405• 42 mph on I-90

• Average speed:• 20 miles in ½ hour = 40 mph

Instantaneous vs. Average