What is Motion?

Motion: A change in position of an object compared to a reference point

Motion involves all of the following: You fill in the blank!

Definition of Motion

Event that involves a change in the position or location of something.

Motion is Relative• Relative – it is described or compared to a

REFERENCE POINThttp://www.classzone.com/books/ml_science_share/vis_sim/mfm05_pg7_relmotion/mfm05_pg7_relmotion.html

• http://www.amnh.org/education/resources/card_frame.php?rid=937&rurlid=894

• Example: Are you moving at this moment? If yes, then how are you moving?

• How does your movement look to another person? (Can they tell you are moving?)

Displacement vs Distance• Displacement - the

distance and direction of an object’s change in position from its starting point

• Distance – how far something moves

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Displacement vs Distance• Displacement - the

distance and direction of an object’s change in position from its starting point

• Distance – how far something moves

• http://www.absorblearning.com/media/item.action?quick=4n#

What is the Displacement?• Problem - A physics teacher

walks 4 meters east, 2 meters south, 4 meters west, and 2 meters north.

• What is the total displacement of the teacher?

• What is the total distanced walked by the teacher?

And the answer is...• Displacement = 0 m - The

teacher has returned to the starting point.

• Distance = 12 meters• The distance is 12 meters but the displacement is

zero. The teacher has “covered 12 meters on the ground”, yet when he is finished walking, he is not walking out of place.

Types of Motion

• Uniform motion - constant speed in a straight line

• Accelerated motion – motion that is changing in speed or direction

• Circular motion - speed is constant but the direction of motion is changing continuously

What is Motion?

SpeedThe rate of change in position

Speed = distance ÷ time or

Speed = distance time

SpeedTypes of Speed

• Average Speed

• Instantaneous Speed

• Constant Speed

SpeedAverage Speed

• Comparison of time and distance– Distance traveled per unit time– Distance is referring to "how much ground an

object has covered" during the time it was in motion.

• S = d / t• T = d / s• D = s x t

SpeedInstantaneous Speed

• Speed at any instant

SpeedConstant Speed

• Speed that does not change– Instantaneous speed that does not change

– Example: After setting cruise control on a car, your speed at any point will be the same until you turn off the cruise control.

What is Motion?

VelocitySpeed plus direction

Example: 50 km/hour north

Velocity

• Speed AND direction -- Velocity must include a speed and a direction.

Displacement is "how far out of place an object is because of its motion”. Displacement is the object's change in position.

What is Motion?

AccelerationThe rate of change in velocityPositive acceleration = speeding upNegative acceleration = slowing down (decelerate)

Acceleration = Vfinal – Vinitial Time or

Acceleration = ∆Velocity Time

Acceleration "the rate at which an object changes its velocity." An object is accelerating if it is changing its velocity.

Acceleration

• A change in velocity– Speeding up

• Positive acceleration

– Slowing down• Negative acceleration• Deceleration

– Changing direction

The Direction of Acceleration

Acceleration will always have a direction associated with it. The direction of acceleration depends on two things:

• whether the object is speeding up or slowing down

• whether the object is moving in the + or - direction

Circular Motion: Continuous

Acceleration

An object traveling in a circular motion is always changing its direction. Therefore, its velocity is always changing, so it is accelerating. This is known as centripetal acceleration.

200m/40s = 5 m/s

2 km/1000s = 0.002 km/s

or 2 m/s

100 m/10 m/s = 10s

50 m/s x 20s = 1000 m

20,000 m/ 40 m/s = 500 s

10m/20s = 0.5 m/s

40 m

40m/40s = 1m/s

25m/10s = 2.5 m/s Steepest line

10m/s 2/ 5 s = 2 m/s10m/s2 x 12s = 120 m/s

10m/s / 2m/s = 5 s

4000m/s /2s = 2000m/s2

40m/s x 10s = 4 m/s2

20m/s x 10s = 2 m/s2

60m/s x 20s = 3 m/s2

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Motion GraphsTime – Distance Graphs

Motion Graph # 1Straight, Flat Line

• As time passes, there is no change in distance; no motion

Motion Graph # 2Straight, Increasing Line

• As time passes, distance increases

• The change in distance is constant – no stopping & starting

Motion Graph # 3Straight, Decreasing Line

• As time passes, distance decreases

• The change in distance is constant

Motion Graph # 4Changing Line

• A changing line means changing distance

• Distance increases then doesn’t change then decreases

Representing Motion in Graphs

Distance – TimeVelocity - Time

Describing a Distance - Time Graph

Describing a Velocity - Time Graph

Speed, Distance, Time Formulas

Calculating SpeedGiven Distance & Time

Divide Distance by Time

Distance ÷ Time = Speed

Speed = Distance ÷ Time

Divide Distance by Time

Distance ÷ Time = Speed

Speed = Distance ÷ Time

Calculating DistanceGiven Speed & Time

Multiply Speed and Time

Distance = Speed X Time

Speed X Time = Distance

Calculating TimeGiven Distance and Speed

Divide Distance by Speed

Distance ÷ Speed = Time

Time = Distance ÷ Speed