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Speed & Velocity. 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 ). Biking Speeds:. 5 meters in 1 second: 5 m/sec
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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)
Biking Speeds: • 5 meters in 1 second: • 5 m/sec • 10 meters in 2 seconds: • 5 m/sec • 20 meters in 10 seconds: • 2 m/sec
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
Instantaneous vs. Average • 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