# Velocity Velocity is speed with a specified direction Velocity is a vector quantity.

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Velocity Velocity is speed with a specified direction Velocity is a vector quantity

Using Vectors Bob walks 10 m East, stops for a while, then continues 7.5 m in the same direction. Where is he then? (What is the result of his motion?) Sue travels 5 miles North, turns around and travels 4 miles South. Where is she then? (What is the result of her motion?)

Using Vectors Karen walks 15 meters due East and then 30 meters due North. What did Karen really accomplish? What is the result of her motion? Pythagorean Theorem (Hyp) 2 = (a) 2 + (b) 2 Can use vectors to combine velocities to find resultant velocity  Treadmill; examples in text

Acceleration An acceleration is a change in velocity.

Acceleration Taylor is driving to work with a speed of 45 mph when she spies a traffic light. Upon noting the traffic light, Taylor removes her foot from the gas pedal. Ten seconds later, she was traveling with a speed of 5 mph. What was Taylor’s average acceleration as she came to a stop?

Acceleration ? A B C

Acceleration If a car initially traveling (on ice) with a constant speed of 5 m/s experiences a constant acceleration of 4.5 m/s 2, how fast would this car be going after 5 s? Would this car travel 138 m during the 5 s?

Acceleration An object with a velocity of 2 m/s experiences an acceleration of 3 m/s 2 for 6s and then experiences an acceleration of 1 m/s 2 for 4s. Does this object slow down during the last 4 s? (Note the velocity and accelerations are all in the same (+) direction.)

Acceleration 1s 3m/s 1s 3m/s 1s 3m/s 1s 3m/s 1s 3m/s 1s 1m/s 1s 1m/s 1s 1m/s 1s 1m/s 1s 3m/s Time elapsed Speed Gained 2m/s 8m/s 11m/s 14m/s 17m/s 20m/s 21m/s 22m/s 23m/s 24m/s 5m/s Speed after time has elapsed Many of us tend to think changes in acceleration mean the same kind of changes in speed – BE CAREFUL – speed and acceleration are NOT the same!

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