10.1 MEASURING MOTION

I CAN…  explain how motion is dependent of the observers frame of reference.  explain motion in terms of position, displacement, velocity, and acceleration which are all vector properties.  draw and interpret motion diagrams to represent position and velocity of an object.  calculate the displacement or change in position of an object.  distinguish between distance and displacement, (speed and velocity)  describe velocity as a vector property that represents the rate at which position changes  calculate average velocity, which may be positive or negative.  recognize the difference between average speed and average velocity.  recognize the difference between instantaneous speed and average speed.  recognize constant velocity on a motion diagram.

MOTION  An object’s change in position relative to a reference point.  You must observe the object in relation to another object that stays in place: stationary object, reference point, or reference frame.  Ex: Comparing a hot air balloons movement to a mountain in the background. (n,s,e,w)

VECTORS  a physical quantity that includes both size and direction.

DISTANCE V. DISPLACEMENT  Distance: the length of the path an object travels  Displacement: is the distance and direction of an object’s final position from its initial position.  Differences:  Distance can be a straight line, but doesn’t have to be.  Displacement must be a straight line. (Displacement may be shorter)  Displacement must include a particular direction.

SPEED  Speed: the distance traveled divided by the time interval during which the motion occurred.  Equation: s=d/t  Units: SI unit for speed is meters per second (m/s).  Will also be seen as km/h or mi/h. Why?  Constant Speed: object covers equal distances in equal amounts of time.  Ex: race car travels a distance of 96 meters every second. Time (s)Distance (m)

DISTANCE-TIME GRAPH  X axis=independent variable, y axis=dependent variable  These lines are representing constant speed.  Which line represents the fastest moving object?  How do you know?  How would an object at rest be represented?

AVERAGE SPEED, INSTANTANEOUS SPEED, VELOCITY  Total distance/Total Time=average speed  Ex: a wheel chair racer finishes a 132 m race in 18s.  v=d/t=132m/18s=__________  7.3m/s  Instantaneous Speed: measured in an infinitely small time interval.  Ex: car speedometer  Velocity: the speed of an object in a particular direction

PRACTICE CALCULATING VELOCITY  Find the velocity in m/s of a baseball thrown 38 m from third base to first base in 1.7 seconds  22m/s toward first base  Metal stakes are sometimes placed in glaciers to help measure a glacier’s movement. For several days in 1936, Alaska’s Black Rapids glacier surged as swiftly as 89 meters per day down the valley. Find the glacier’s velocity in m/s.