Review of Distance vs Displacement and Velocity vs Speed Graham Oakley 2015

Types of Quantities Vector – Quantities that includes both magnitude and a direction Vectors can be drawn They are represented by arrows Example: 12 m south Scalar – Quantities that do not include direction (magnitude only) Example: 4 seconds

Distance vs. Displacement What two changes help you identify that an object is in motion? Change in Direction Change in Speed

_______________ is necessary to determine if something is in motion. Frame of Reference: background that appears to be stationary to a moving object Earth is the most common frame of reference.

How can something appear to be motionless but actually be moving? If an object has the same frame of reference. If the object is moving at the same speed. Examples?

Explain how an object can have a zero or negative displacement. Dist. Vs. Disp. Distance Actual path that an object takes Cannot be negative Displacement Straight line from start to finish Can be negative or zero Think about your charts made to calculate distance and displacement on the grid. Explain how an object can have a zero or negative displacement.

Distance vs Displacement Distance is a scalar quantity: direction doesn’t matter Displacement is a vector Direction matters Straight line route from where you started to where you end (as the crow flies) MUST HAVE A DIRECTION

Explain how an object can have a zero or negative displacement. Dist. Vs. Disp. Distance Actual path that an object takes Cannot be negative Displacement Straight line from start to finish Can be negative or zero Think about your charts made to calculate distance and displacement on the grid. Explain how an object can have a zero or negative displacement.

What is the Distance traveled? 8 m 6 m 2 m 1 m d = 8 m + 6 m + 2 m + 1 m d = 17 m

What is the displacement? - 8 m 6 m 2 m 1 m

Distance vs. Displacement Examples Distance= Displacement = 9 m 9 m right 3 m 6 m Distance= Displacement = 9 m 3 m left Distance= Displacement = 9 m ? 3 m 6 m

Distance versus Displacement To determine displacement draw a diagram of the path taken Example: 8 m east, then 6m north, then 2 m east, then 1 m south Simplify the diagram to a right triangle Use Pythagorean Theorem to determine the displacement 8 m 6 m 2 m 1 m 8 m 6 m 2 m 1 m 10 m 5 m

Range of Values Maximum Displacement occurs when: The two vectors are pointed in the same direction (0o) Example: Displacement = 10 m Minimum Displacement occurs when: The two vectors are pointed in the opposite directions (180o) Displacement= 6 m Right All other angles will result in a value in between that range. 8 m 2 m 8 m 2 m

Example with Word Problems A turtle crawls 5m north, then 3m east, and then 2 m south in 1000 seconds. What is his distance traveled, displacement, average speed and average velocity? Givens: t=1000 s 5 m 3 m 2 m

Distance vs Displacement 5m +3m +2m = 10 m Displacement= a2 + b2 = c2 (3m)2 +(3m)2 = c2 18 m2 = c2 c = 4.2 m Northeast 3 m

Speed vs Velocity Speed: Speed is a scalar, need to use distance Velocity is a vector, need to use displacement