Velocity (AP) - Kinematics | Show Me The Physics

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Honors Extension

FrameRef_WallMoves.mov

Watch the Animation Below

A curveball has more than one measurable motion. How many does it have? (ignore spin)

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3 Motions

Forward, Left (or Right), Down

Velocity - Speed in a Particular Direction

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C. Velocity

Speed in a particular direction

Football player running to catch the ball

Velocity & Direction

Focus on the man walking across this page. Identify his 2 velocities. Which is the greater of the two?

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The answer depends on your coordinate system. The man is moving to the north (or up, forward, y) and the east (or across, to the right, x). Since his easterly displacement is greater, he has a greater easterly velocity.

Ex) Joe Drove 13 Meters Northeast in 2.0 Seconds

What was Joe's...

Northeast displacement? displacement east? displacement north?

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Northeast displacement? 13 m displacement east? 12 m E displacement north? 5 m N

We can say that Joe has 3 velocities:

V = 6.5 m/s N.E.

V = 5 m North / 2 seconds
= 2.5 m/s North

V = 12 m East / 2 seconds
= 6 m/s East

1. Velocity Is Always Written With Direction

Examples: 5 m/s east • +5 m/s • 100 m/s downward • −100 m/s

2. Equation

V = Δd/Δt

d = displacement

Ex

Given

A car travels 90. m due north in 15 secs, and turns around and travels 40. m due south in 5.0 secs.
Find: what is the average velocity of the car?

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V = (50. m N) / (20. sec)

V = 2.5 m/s North

Check Your Understanding

5 quick questions — pick an answer to see if you’re right.

1. A car drives 60. m east in 10. s, then turns and drives 20. m west in 10. s. What is its average velocity?

2. For the same car (60. m east in 10. s, then 20. m west in 10. s), what is its average speed?

3. Joe drives 13 m northeast in 2.0 s, which is 12 m east and 5.0 m north. What is Joe's northward velocity?

4. In the equation V = Δd/Δt, what does d stand for?

5. Ignoring spin, a curveball moves forward, sideways, and down at once. How many velocities does it have?

Acceleration →