Determining Position “Hey, Is This Thing Moving?”

Position Position is defined relative to a reference point and reference directions.

Reference Points and Reference Directions Three things must be included: 1.) A reference point – a starting point used to describe the position of an object. 2.) A reference direction that describes which way to move in relation to the reference object. 3.) A distance from the reference point.

Reference Points and Reference Directions The flagpole can be used as a reference point for finding the bicycle. (Can you give directions to locate the bike?)

Reference Points and Reference Directions A plus sign (+) indicates movement in the direction of the reference point. A minus sign (–) indicates movement in the direction opposite of the reference point. The description of an object’s motion also depends on the reference point chosen.

Position as a Vector A vector is a quantity in which two things must be specified: Distance from the reference point (represented by the length of the arrow) Direction from the reference point (represented by the direction the arrow is pointing)

Positions in Two Dimensions Objects that do not move in straight lines require two reference directions. A car traveling from San Diego to Sacramento doesn’t move in a straight line. (What direction would we say it is traveling?)

Positions in Two Dimensions In this map of a city, the art museum is located ___________m west and ___________m south of the bus station. 1,

Changing Position The change in an object’s position is called its displacement.

Changing Position Displacement is the difference between the initial position and the final position of an object.

Changing Position Displacement includes a size and a direction. Displacement is a vector.

Changing Position Direction of displacement is the direction from starting point to end point. Size of displacement is the distance from the starting point to the ending point.

Distance and Displacement Distance __________ Displacement __________ 40 m 40 m East

Distance and Displacement Distance __________ Displacement ________________ 70 m 50 m Northeast

Distance and Displacement Distance __________ Displacement _________ 140 m 0 m

Displacement is a(n) ____ because it has both size and direction. Aspeed Bvelocity Cvector Dacceleration 1.1 Determining Position

Position is defined relative to ____. Aa reference point and a vector Bdisplacement and reference directions Ca vector and reference directions Da reference point and reference directions 1.1 Determining Position

Which of the following statements is true? ADisplacement and distance traveled are always the same. BDisplacement and distance traveled are never the same. CDistance traveled is the direction of the displacement vector. DDisplacement and distance traveled are the same if the direction does not change. 1.1 Determining Position

What must you have to determine a position? Aacceleration Bvelocity and speed Creference point and origin Dreference point and reference direction SCI 1.a