# Do Now 1/31  Yesterday you calculated speed in the bubble gum lab, explain in words what speed is a measure of.

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Do Now 1/31  Yesterday you calculated speed in the bubble gum lab, explain in words what speed is a measure of

Speed and Velocity 11.2

Speed  Put in order of fastest to slowest  Grass growing, leaf falling, car driving, bird flying

Speed  Car, bird, leaf, grass  The differences among these types of motion can be described in terms of speed  Speed is the ratio of the distance an object moves to the amount of time the object moves  SI unit is meters per second (m/s)

Two ways to express speed  Average speed- is computed for the entire duration of a trip  Tells how fast something moves for an entire trip  Ex: hiker in the mountains Average speed = total distance total time total time v = d t

 Instantaneous speed (v)- measured at a particular instant  A car’s speedometer gives instantaneous speed

Graphing Motion  A distance-time graph is a good way to describe motion  The slope of the line on a distance time graph is the speed of the object traveling  Slope is rise/run  y 2 -y 1 x 2 -x 1 x 2 -x 1

Velocity  The speed and direction that an object is traveling is its velocity  Velocity is a vector and velocities can be combined using vector addition

Try It  An Olympic swimmer swims 50.0meters in 23.1 seconds. What is his average speed?  A plane’s average speed is 600km/h. If the trip takes 2.5 hours, how far does the plane fly? (hint: change the average speed formula around to solve for d)

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