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