Vectors: Displacement and Velocity

Vectors Examples of vectors: displacement velocity acceleration

Displacement Example: Ms. Rosebery walks 2 m [East] and then 1 m [West]. What was her distance travelled? What was her displacement?

Displacement Example: Ms. Rosebery walks 2 m [East] and then 1 m [West]. What was her distance travelled? What was her displacement? Distance travelled:  d = 2 m + 1 m = 3 m

Displacement Example: Ms. Rosebery walks 2 m [East] and then 1 m [West]. What was her distance travelled? What was her displacement? Distance travelled:  d = 2 m + 1 m = 3 m Displacement: 2 m 1 m

Displacement Example: Ms. Rosebery walks 2 m [East] and then 1 m [West]. What was her distance travelled? What was her displacement? Distance travelled:  d = 2 m + 1 m = 3 m Displacement: She is 1 m [East] of her original starting position. 2 m 1 m

Displacement We can represent [East] as the positive direction and [West] as the negative direction: 2 m 1 m

Displacement We can represent [East] as the positive direction and [West] as the negative direction: = 2 m [East] + 1 m [West] = + 2 m – 1 m 2 m 1 m

Displacement We can represent [East] as the positive direction and [West] as the negative direction: = 2 m [East] + 1 m [West] = + 2 m – 1 m = + 1 m 2 m 1 m

Displacement We can represent [East] as the positive direction and [West] as the negative direction: = 2 m [East] + 1 m [West] = + 2 m – 1 m = + 1 m = 1 m [East] 2 m 1 m

Directions It is conventional to represent the following directions as positive: forward forward right right up up North North East East

Velocity Velocity is similarly not simply speed + a direction.

Velocity Example: Ms. Rosebery walks 2 m [East] and then 1 m [West] in 3 s. What was her average speed? What was her average velocity?

Velocity Example: Ms. Rosebery walks 2 m [East] and then 1 m [West] in 3 s. What was her average speed? What was her average velocity?

Velocity Example: Ms. Rosebery walks 2 m [East] and then 1 m [West] in 3 s. What was her average speed? What was her average velocity?

Instantaneous Velocity Average velocity is rarely calculated for an object changing direction. It makes more sense to talk about the instantaneous velocity, which is the speed + the direction at that particular instant.

10m due North + 7m due South 10m due North + 7m due South 15km due East + 20km due West + 55km due East