The Language of Motion Sally and John need to go to the store. Sally goes to the store 2 km away and comes straight home. John goes to the store 4 km away. Who travelled the furthest?

Direction Makes a Difference Quantities that refer to the size of a measurement, or magnitude, are called scalars. Examples: 1 cm, 5 km, 2 hours Quantities that describe magnitude and also include direction are called vectors. Example: 1 cm higher, 5 km East, 2 hours before the show Determine whether the following is a scalar or a vector: Susan walked 2.1 km to get to her school. Turn left at the end of the street. The car odometer reads 13,000 km. The show starts at 30 minutes past the hour. The boat travelled east at 20 km/h. scalar vector scalar vector vector

Distance and Position A position is a vector quantity that describes a specific point relative to a reference point. Describes an object’s location as seen by an observer from a particular viewpoint. Any point can be chosen as a reference. Example: The school is 3 km east of my house. Activity! Using yourself as a reference point, identify different students that have the following position relative to you (if there is no one, simply write “none”).

The SI unit for both distance and position is metres, m. Distance (d) is a scalar quantity that describes the length of a path between two points or locations. Example: A person ran a distance of 400 m. The SI unit for both distance and position is metres, m. Using “Home” as a reference point… Using “Home” as a reference point… Position: 10 km east of home Position: 0 km Distance: 10 km Distance: 20 km Using “Store” as a reference point… Using “Store” as a reference point… Position: 0 km Position: 10 km west of store Distance: 20 km Distance: 10 km

Displacement and Distance Displacement describes the straight-line distance and direction from one point to another. Displacement describes how much an object’s position has changed. Displacement is equal to the final position minus the initial position. The SI unit for displacement is metres, m. Between 2 s and 5 s the skateboarder’s displacement is 5 m [E]. The skateboarder’s distance travelled is 5 m. See page 349

Watch for Signs When using vector quantities, opposite directions are given opposite signs. Common sign conventions

Displacement and Distance 1. Judy walks 0.5km to her friend’s house and then comes back home. a) What is her total distance that she walked? b) What is her total displacement? 0.5 km there + 0.5 km back = total of 1 km (distance  no direction) Object ended up back where it started  displacement = 0 km Judy rides her bike to the store, which is 2km east of her house. She then drops by her cousin’s house, which is 3km west of the store. Draw a picture of her travels What is the total distance she traveled? What is her total displacement? 2 km to store + 3 km to cousin’s house = total of 5 km (no direction!) Δd = df – di di = 0 km; df = -1 km or 1 km [W] Δd = 1 km [W] – 0 km = -1km – 0 km = - 1 km or 1 km [W]