MotionMotion11.1 Distance and 11.1 Distance and

DisplacementDisplacement Chapter 11Chapter 11

What are we going to learn?What are we going to learn?►Methods of describing motionMethods of describing motion►How can vectors be combined?How can vectors be combined?

A story of motion...A story of motion...►Once upon a time, 3 students (George, Once upon a time, 3 students (George,

Harry, and William) were on their way to Harry, and William) were on their way to school. When asked the question, “How school. When asked the question, “How fast are your friends moving?” there were fast are your friends moving?” there were very different and conflicting answers very different and conflicting answers from the students. from the students.

►George says that Harry and William are George says that Harry and William are moving very fast.moving very fast.

►Harry says that George is moving but Harry says that George is moving but William is not. William is not.

►William says that George is moving but William says that George is moving but Harry is not. Harry is not.

► If everyone is telling the truth, how can If everyone is telling the truth, how can this be?this be?

► It’s all a matter of It’s all a matter of frame of referenceframe of reference...... ►Hint........Hint........

►George is standing waiting at the bus George is standing waiting at the bus stop. Harry and William are already on a stop. Harry and William are already on a moving bus.moving bus.

Frame of ReferenceFrame of Reference►NecessaryNecessary to describe motion to describe motion accuratelyaccurately

and and completelycompletely►A system of A system of objectsobjects that are that are not movingnot moving

with respect to with respect to one anotherone another

Relative MotionRelative Motion►MovementMovement in relation to a in relation to a frame of frame of

referencereference

►More on this later.....More on this later.....

Distance Distance ►LengthLength of the of the pathpath between between two points two points

Distance UnitsDistance Units►SI unitSI unit for distance: for distance: metermeter (m) (m) ►For very For very largelarge distances: distances: kilometerskilometers (km) (km)►For distances For distances smallersmaller than meters: than meters:

centimeters centimeters (cm)(cm)

DisplacementDisplacement►DirectionDirection from the from the starting pointstarting point and the and the

length of a length of a straight linestraight line from the starting from the starting point to the point to the ending pointending point

►Gives information both about Gives information both about how far how far awayaway an an object isobject is from a given point and from a given point and in what in what directiondirection the object is the object is from that point from that point

►Displacement is a Displacement is a vectorvector

VectorsVectors►A quantity that has A quantity that has directiondirection and and

magnitudemagnitude (can be (can be sizesize, , lengthlength, or , or amountamount))

►Add displacements using Add displacements using vector additionvector addition

Vector AdditionVector Addition►When two vectors have the When two vectors have the same same

directiondirection, you can , you can add their magnitudesadd their magnitudes

►When two vectors are in When two vectors are in opposite opposite directionsdirections, , subtractsubtract one one magnitudemagnitude from from the otherthe other

Ex: A police officer going the speed limit of Ex: A police officer going the speed limit of 45 mph clocks you going in the opposite 45 mph clocks you going in the opposite direction at 92 mph. direction at 92 mph. Do you get a ticket?Do you get a ticket?

►Since the vehicles are going in Since the vehicles are going in oppositeopposite directionsdirections, subtract the police officer , subtract the police officer vector from your vehicle vector...the vector from your vehicle vector...the answeranswer is your is your unknown speedunknown speed

►92 mph – 45 mph = 47 mph 92 mph – 45 mph = 47 mph ((2 mph over the speed limit2 mph over the speed limit))

►When When two or moretwo or more vectors have vectors have different different directionsdirections, combine them by , combine them by graphinggraphing

Vector AdditionVector Addition►Sum of two or more vectorsSum of two or more vectors is the is the

resultant resultant vectorvector

Review QuestionsReview Questions►What two things must you know to What two things must you know to

describe the motion of an object?describe the motion of an object?

Review QuestionsReview Questions►What two things must you know to What two things must you know to

describe the motion of an object?describe the motion of an object?Frame of reference and directionFrame of reference and direction

►True or false? True or false? A frame of reference is not necessary to A frame of reference is not necessary to

describe motion accurately and describe motion accurately and completely.completely.

►True or false? True or false? A frame of reference is not necessary to A frame of reference is not necessary to

describe motion accurately and describe motion accurately and completely.completely.

False, frame of reference is necessary to False, frame of reference is necessary to accurately describe motionaccurately describe motion

►True or false? True or false? Five blocks south is an example of a Five blocks south is an example of a

displacement. displacement.

►True or false? True or false? Five blocks south is an example of a Five blocks south is an example of a

displacement. displacement. TrueTrue

►Circle the letter of the SI unit best suited Circle the letter of the SI unit best suited for measuring the length of a room in for measuring the length of a room in your home.your home.

a. kilometersa. kilometers b. metersb. metersc. centimetersc. centimeters d. millimetersd. millimeters

►Circle the letter of the SI unit best suited Circle the letter of the SI unit best suited for measuring the length of a room in for measuring the length of a room in your home.your home.

a. kilometersa. kilometers b. metersb. metersc. centimetersc. centimeters d. millimetersd. millimeters

► Imagine that you are a passenger in a Imagine that you are a passenger in a car. Circle the letter of the best frame of car. Circle the letter of the best frame of reference you could use to determine reference you could use to determine how fast the car is moving relative to the how fast the car is moving relative to the ground.ground.

a.a. the people sitting next to you in the the people sitting next to you in the backseatbackseat

b. the driver of the carb. the driver of the carc.c. a van traveling in the lane next to a van traveling in the lane next to

your caryour card. a sign post on the side of the roadd. a sign post on the side of the road

► Imagine that you are a passenger in a Imagine that you are a passenger in a car. Circle the letter of the best frame of car. Circle the letter of the best frame of reference you could use to determine reference you could use to determine how fast the car is moving relative to the how fast the car is moving relative to the ground.ground.

a.a. the people sitting next to you in the the people sitting next to you in the backseatbackseat

b. the driver of the carb. the driver of the carc.c. a van traveling in the lane next to a van traveling in the lane next to

your caryour card. a sign post on the side of the roadd. a sign post on the side of the road

►What would your total displacement be if What would your total displacement be if you walked from your front door, around you walked from your front door, around the block, and then stopped when you the block, and then stopped when you reached your front door again?reached your front door again?

a. one blocka. one block b. two b. two blocksblocks

c. the entire distance of your tripc. the entire distance of your tripd. zerod. zero

►What would your total displacement be if What would your total displacement be if you walked from your front door, around you walked from your front door, around the block, and then stopped when you the block, and then stopped when you reached your front door again?reached your front door again?

a. one blocka. one block b. two b. two blocksblocks

c. the entire distance of your tripc. the entire distance of your tripd. zerod. zero

► Compare and contrast distance and Compare and contrast distance and displacement. displacement.

► Compare and contrast distance and Compare and contrast distance and displacement. displacement.

Same: both describe measurement of Same: both describe measurement of motionmotion

Different: distance is a straight line Different: distance is a straight line measurement between 2 pointsmeasurement between 2 points

displacement includes direction displacement includes direction and a straight line measurement from and a straight line measurement from starting point to finish point starting point to finish point

► A vector is a quantity that has both A vector is a quantity that has both ______________ and ______________.______________ and ______________.

► A vector is a quantity that has both A vector is a quantity that has both magnitudemagnitude and and directiondirection..

► The vector sum of two or more other The vector sum of two or more other vectors is called the vectors is called the _________________________. _________________________.

► The vector sum of two or more other The vector sum of two or more other vectors is called the vectors is called the resultant vectorresultant vector. .

► Circle the letter of each answer that Circle the letter of each answer that could describe the magnitude of a could describe the magnitude of a vector.vector.

a. length b. direction c. amount d. a. length b. direction c. amount d. sizesize

► Circle the letter of each answer that Circle the letter of each answer that could describe the magnitude of a could describe the magnitude of a vector.vector.

a. lengtha. length b. direction b. direction c. amount d. c. amount d. sizesize

►Because the two displacements are in Because the two displacements are in opposite directions, the magnitude of the opposite directions, the magnitude of the total displacement is total displacement is ________________________ .________________________ .

►Because the two displacements are in Because the two displacements are in opposite directions, the magnitude of the opposite directions, the magnitude of the total displacement is total displacement is addition of opposite addition of opposite vectors with a total displacement of 4 kmvectors with a total displacement of 4 km..

►Circle the letter that answers the Circle the letter that answers the question. What is the displacement of a question. What is the displacement of a cyclist who travels 1 mile north, then 1 cyclist who travels 1 mile north, then 1 mile east, and finally 1 mile south?mile east, and finally 1 mile south?

a. 3 miles easta. 3 miles east b. 1 mile northb. 1 mile northc. 3 miles southc. 3 miles south d. 1 mile eastd. 1 mile east

►Circle the letter that answers the Circle the letter that answers the question. What is the displacement of a question. What is the displacement of a cyclist who travels 1 mile north, then 1 cyclist who travels 1 mile north, then 1 mile east, and finally 1 mile south?mile east, and finally 1 mile south?

a. 3 miles easta. 3 miles east b. 1 mile northb. 1 mile northc. 3 miles southc. 3 miles south d. 1 mile eastd. 1 mile east