# Velocity-Time(VT) Graphs Mr. Fedell

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Velocity-Time(VT) Graphs Mr. Fedell

VT vs. PT graphs A position-time (PT) graph tells you where an object is. A velocity-time graph tells you how fast it’s moving. **(VT graphs DO NOT give in position info!)**

When an object stays still for 10s, its velocity is 0 m/s.

Constant Velocity CV –AWAY CV-TOWARDS

Speeding up or Slowing down Speed up – away away Speed up – toward toward Slow down – Slow down -

This may help AWAY STILL TOWARDS

V vs. T Graphs WS Practice!

V vs. T Graphs WS KEY!

PT and VT – Motion Detector Lab File Open Additional Physics Real Time physics Mechanics Open file “Constant Velocity” Extend data collection from 5-10 seconds. - Capture the PT and VT for a JEEP backflip - Sketch well-labeled graphs. Label parts as CV-away, still, CV-towards - Obtain the slope of the PT on both the CV away and CV towards sections, compare with your VT graph! (show all work below)

This may help AWAY STILL TOWARDS

“Racing Questions” In this race, who is: a) Moving faster i. at 0 seconds? ii. at 5 seconds? iii. at 10 seconds? b) Moving with a positive velocity? c) What does the intersection indicate? d)Who started “ahead”?

Practice – Racing problems!

Converting from POSITION to VELOCITY Graphs The slope of a P-T graph is the velocity.

Making a VT from a PT 40 0 m/s 30 20 -10 m/s 10 0 m/s Velocity (m/s) 20 m/s 0 -10 -20 -30 -40

Practice - Page 3

Page 3 - KEY See white board.

Velocity from Position – Motion Detector Lab File Open Additional Physics Real Time physics Mechanics Open file “Velocity from Position” - Sketch well-labeled PT and VT graphs for CV-Away, Still, and CV-Towards

Concept Review What information can we gather from a PT? What value does slope represent? A negative slope indicates what? What information can we gather from a VT? Can we obtain position information from a VT? What is indicated when an objects velocity goes from to – ? What value might slope represent? (units?)

More Practice!!!

SLOPES! The slope of PT graph gives the velocity (m/s). The slope of a VT graph gives the acceleration (change in velocity) Includes both SPEED UP and SLOW DOWN Unit for acceleration m/s2 or m/s/s

SLOPES! So what does an acceleration of 1 m/s2 mean? How about 5 m/s2 ? Kingda Ka: 11 m/s2 !!!

SLOPES! A slope of ZERO indicates CONSTANT VELOCITY or STILL Still CV-AWAY CV-Towards

SLOPES! A steeper slope the higher the acceleration. It’s the more QUICKLY and object can CHANGE its VELOCITY. Motorcycle 18 Wheeler

For this velocity-time graph Velocity (m/s) 0 - Still CV Speed up Slow down Changing velocity Object is moving fastest Moving away Moving towards

For this velocity-time graph 80 60 40 20 Velocity (m/s) 0 -20 -40 - 60 - 80 When does this object change direction!?

Graph Matching Lab 1. File Open EAS SHARES Drive Bauer STU SHARE Logger Pro Files Graph Matching Folder 2. Your group’s job is to match graphs 1-3!

Practice Quiz Question #1 At rest Constant velocity Speeding up Slowing down Moving away from the origin Moving towards the origin Farthest distance from the origin

Practice Quiz Question #2 40 35 Initial position? 30 25 Final position? 20 15 Displacement? 10 5 Velocity at each stage?

Practice Quiz Question #3 8 6 4 A 2 Velocity (m/s) 0 -2 -4 -6 -8 B C D E F G At rest Constant velocity Speeding up Slowing down Moving away from the origin Moving towards the origin Farthest distance from the origin

Draw the PT for the following scenario: You You You You You walk to Java City for 5s slow down as you approach the line for 5s wait in line for 5s turn around and speed up for 5s walk at a constant velocity for 5s

Convert the PT from last slide to a VT

Sign of Velocity and Acceleration If an object has zero acceleration, it is: 1. Still 2. CV-AWAY 3. CV-TOWARDS Change in velocity (slope of a VT graph)

Acceleration has a direction It’s not always pointing in the same direction you’re moving Scenario 1: Speeding up (gas pedal) Velocity Scenario 2: Slowing Down (brakes) Velocity Acceleration - Acceleration

Sign of Velocity and Acceleration If you are accelerating in the SAME direction you’re moving Speeding Up Reverse Forward V (-) V ( ) a (-) a ( ) If you are accelerating in the OPPOSITE direction you’re moving Slowing Down Reverse Forward V (-) V ( ) a ( ) a (-)