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Speed and Velocity 11.2 Page 332-337

SPEED •  Speed is the RATIO of the distance an

object moves over the amount of time the object moves

•  SI Units = Meters per second (m/s)

Average Speed •  Average speed is computed for the entire

duration of a trip, and instantaneous speed is measured at a particular instant. – Average speed: Driving to the mall 25 mi/hr,

hit stop lights, freeway 55 mi/hr, off ramp 25 mi/hr, stop lights, slow in the parking lot.

–  Instantaneous speed: When police officers tag cars for speeding they are measuring the speed at that moment in time

Average Speed Average Speed = total distance

total time v = d t

Pg 333 Example: You travel 35 kilometers in 0.4 hours and then

you travel 53 kilometers in 0.6 hours. What is your average speed for the entire trip? Total distance = 35 km + 53 km = 88km Total time 0.4 h + 0.6 h 1.0 h = 88 km = 88 km/hr 1.0 h

or

Instantaneous Speed •  The rate at which an object is moving at a given

moment in time –  When police officers tag cars for speeding they are

measuring the speed at that moment in time

Graphing Motion •  Slope of a line on a

distance-time graph is the object’s speed

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Distance-Time Graph • Faster the speed -- the steeper the line • Curved line -- the speed is increasing or decreasing • Straight line -- constant speed

Velocity •  The speed and direction in which an

object is moving – Speed in a given direction

•  Description of Speed AND direction of motion

Combining Velocities •  Combine velocities using vector addition. Two or

more velocities add by vector addition –  Add velocities in the same direction –  Subtract velocities in opposite directions

Current 3 m/s

Swimmer 2 m/s

Total velocity of swimmer = 5 m/s

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Combining velocities that are not in a straight line

•  You can determine the resultant velocity of the boat relative to the riverbank by measuring from the tail of one vector to the head of the other

QUESTOINS?? Pg 333 - Extra practice = answer the

practice problems Homework: Worksheet 11.2 - Speed and

Velocity