2.2 velocity Speed The average speed of an object is defined as the total distance traveled divided by the total time elapsed Average peea、 total distance total time Speed is a scalar quantity
2.2 velocity Speed ◼ The average speed of an object is defined as the total distance traveled divided by the total time elapsed ◼ Speed is a scalar quantity = = total distance Average speed total time d v t
Speed, cont Average speed totally ignores any variations in the objects actua motion during the trip The total distance and the total time are all that is important Si units are m/s
Speed, cont ◼ Average speed totally ignores any variations in the object’s actual motion during the trip ◼ The total distance and the total time are all that is important ◼ SI units are m/s
Velocity It takes time for an object to undergo a displacement The average velocity is rate at which the displacement occurs △XX-X average △tt-t generally use a time interval,So let t= 0
Velocity ◼ It takes time for an object to undergo a displacement ◼ The average velocity is rate at which the displacement occurs ◼ generally use a time interval, so let ti = 0 − = = − f i average f i x x x v t t t
∨ elocity continued a Direction will be the same as the direction of the displacement(time interval is always positive) t -is sufficient Units of velocity are m/s(sI) cm/s(cgs)or ft/s(US Cust.) a other units may be given in a problem but generally will need to be converted to these
Velocity continued ◼ Direction will be the same as the direction of the displacement (time interval is always positive) ◼ + or - is sufficient ◼ Units of velocity are m/s (SI), cm/s (cgs) or ft/s (US Cust.) ◼ Other units may be given in a problem, but generally will need to be converted to these
Speed vs. velocity 0 2006 Brooks/Cole- Thomson Cars on both paths have the same average velocity since they had the same displacement in the same time interval The car on the blue path will have a greater average speed since the distance it traveled is larger
Speed vs. Velocity ◼ Cars on both paths have the same average velocity since they had the same displacement in the same time interval ◼ The car on the blue path will have a greater average speed since the distance it traveled is larger