Motion
Chapter 10Section 1 Measuring MotionPAGES 316-324
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Objectives
Explain the relationship between motion and a frame of reference.Relate speed to distance and timeDistinguish between speed and velocitySolve problems related to time, distance, displacement, speed and velocity
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Observing Motion
Motion is described in relation to another object that stays in place– a stationary objectThe stationary object is a reference point sometime is called a reference frame or frame of reference
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Distance
Distance measures the path taken
A
B
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Displacement-the change in position of an object
A straight line between the start and finish
Difference is straightness and direction Toward B
A
B
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Distance vs Displacement
Project
Design a demonstration that illustrates the difference between distance and displacementYou may use a toy car, airplane, rat, use your imagination
Be ready to present next class!
Speed
Speed describes how fast something moves
Speed the distance traveled divided by the time interval
S = d/t for example 5m/sMeters / second the slash is read per
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Time Distance Graph
Slope of the line is the object’s speed28
Dependent variable
independent variable
Constant speed
The speed does not change
Most objects do not move with constant speed
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Instantaneous Speed
The speed at a given point in time
NASCAR 173.45 MPHThe car’s speed at that instant
A car’s speedometer
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Speed
Speed-- how fast something is goingSpeed is a scalar quantity.Scalar tells the amount of something
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Formula—
Time is measured inSeconds or hoursDistance is measured incm, km, or m50 km—d 2 hrs—tHow fast—speed50km/2hr=25km/hr
s=d/t
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Velocity
Velocity is speed and directionVelocity is a vector quantity.A vector shows speed and direction.Vectors are arrows that show direction.
Velocity
Velocity is speed and directionVelocity is a vector quantity.A vector shows speed and direction.Vectors are arrows that show direction.
Does your velocity change?
Yes . . . Because the direction changed and velocity includes both speed and direction
Draw an arrow over the number indicating speed
50m/s
Velocity Vectors
Velocity uses the same units butcan include a vector arrow that
indicates direction
Velocity Vectors
80 120
100
With the windSame--Add
Against the windopposite--subtract
100
20
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Worksheet Velocity
Note the longer the line the faster you are goingThe shorter the slower
Using vectors
Parallelogram rule: when given two vectors draw parallel lines.
The diagonal of the parallelogram is the resultant
Velocity
Speed and directionVelocity is a vector quantity.
Escaped lionYou need to know his speed and direction!!!!
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Velocity Vectors
A vector shows the direction and magnitude (speed) of an object
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Draw an arrow over the number indicating direction and
approximate speed
50m/s
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Velocity Velocity uses the same units as speeduses the same units as speed butbut
can include a vector arrow that can include a vector arrow that indicates directionindicates direction
Using vectors
Parallelogram rule: when given two vectors draw parallel lines.The diagonal of the parallelogram is the resultant
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Velocity Vectors
80 120
100
With the windSame--Add
Against the windopposite--subtract
100
20
20
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Freefall -- an object falling free of all restraint
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V=atVelocity = acceleration times the
time
a– accelerationt – time
Acceleration due to gravity is 9.8m/s2
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How fast? v=at
0s 1s 2s 3s 4s 5s 6s 7s 8s
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Distance of Fall
0 1 2 3 4 5 6 7 8
D=1/2at2
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Freefallspeedometer—shows how fast
odometer—shows how far
Two equationsv=at and d=1/2at2
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Freefall assignment
d= how far? d=1/2at2
0s 1s 2s 3s 4s 5s v= how fast v=atWrite in the seconds at the bottom
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