Scalars and Vectors in Motion

Scalars vs. Vectors Scalars vs. Vectors Scalar Quantity – physical quantity with Magnitude Example: Temperature Vector Quantity – physical quantity with 1) Magnitude (Size) 2) Direction Example: Force

Vector Sign Conventions + Up Down Right Left + _ + + _ _ _

Describing an Object’s Change in Position How many ways can you get from point A to point B? A B

Distance vs. Displacement (d) (Δx) The path-length of an object in motion

Displacement (Δx)– a vector that represents the change in position Can displacement be negative? Yes if xi > xf Ex: moving left

Discuss the red devil’s motion (quantitatively) with a partner Discuss the red devil’s motion (quantitatively) with a partner. Use the terms position, displacement, distance. x (m)

Speed vs. Velocity (v) How fast an object is travelling Ex: 6 m/s How fast an object is travelling… in a specific direction Ex: 6 m/s downwards

If a buggy drove in reverse would it have a negative velocity? 5 m/s Speed = 5 m/s Velocity = +5 m/s Speed = 5 m/s Velocity = -5 m/s 5 m/s If a buggy drove in reverse would it have a negative velocity? Not if the buggy was reversing to the right/East!

Instantaneous and Average Instantaneous speed/velocity is speed at a particular instant in time Average speed/velocity is speed over whole journey

Calculating Average Speed and Velocity When would these two quantities be the same value? When would these two quantities be different? Object moves in only 1 Direction Object turns around

In Rio, Katie Ledecky broke her own world record in the 800-meter freestyle, finishing in 8 min 7 seconds. What was Katie’s average speed and velocity?

Getting a Feel for m/s Convert 1 m/s into miles per hour: >20 mph So if you have a speed of 10 m/s, roughly how many mph is that? Or if you are driving 65 mph, roughly how many m/s is that? >20 mph >32.5 mps