5 meters in 1 second: 5 m/sec 10 meters in 2 seconds: 5 m/sec 20 meters in 10 seconds: 2 m/sec...
TRANSCRIPT
• 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