Position, Speed, and Velocity Opener: Ms. Erdelyi’s dog, Roxy, is practicing for her agility competition. She leaves Ms. Erdelyi’s side and runs 80 m due west to pick up a ball. She carries the ball 27 m due east and drops it into a bucket. What is Roxy’s displacement?

Average Speed Average speed = 𝑡𝑜𝑡𝑎𝑙 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑒𝑑 𝑡𝑜𝑡𝑎𝑙 𝑡𝑖𝑚𝑒 𝑒𝑙𝑎𝑝𝑠𝑒𝑑 SI unit: 𝑚 𝑠 Represented as: 𝑉 𝑎𝑣 = ∆𝑑 ∆𝑡 Distance (scalar) Change in time (scalar) ∴𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑠𝑝𝑒𝑒𝑑 𝑖𝑠 𝑎 𝑠𝑐𝑎𝑙𝑎𝑟 𝑞𝑢𝑎𝑛𝑡𝑖𝑡𝑦

example A dog runs 43 m in a straight line. It takes 28 s. Calculate the dog’s average speed. 𝑉 𝑎𝑣 = ∆𝑑 ∆𝑡 𝑉 𝑎𝑣 = 43𝑚 28𝑠 𝑉 𝑎𝑣 = 1.6 𝑚/𝑠

example How far will a cheese roll travel in 15s if it rolls at 3.8 m/s? 𝑉 𝑎𝑣 = ∆𝑑 ∆𝑡 𝑉 𝑎𝑣 (∆𝑡)= ∆𝑑 3.8 m/s(15𝑠)= ∆𝑑 57 m= ∆𝑑

Average Velocity 𝑉 𝑎𝑣 = total displacement (or change in position) 𝑡𝑜𝑡𝑎𝑙 𝑡𝑖𝑚𝑒 𝑓𝑜𝑟 𝑡ℎ𝑎𝑡 𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡

Average Velocity Example: Mr. Fredricksen’s house rises 82m [up] in 15 s. What is its average velocity?

An ice cream truck travels at 22 An ice cream truck travels at 22.3 km/h [W] trying to escape a swarm of angry bees. How long will it take the truck to travel 241 m [W] to safety?

Position-time graphs Describes the motion of an object Straight line indicates constant velocity (object not accelerating) To the SMART file