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 Slow down – away Speed up – toward Slow down - toward

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: 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 0 m/s -10 m/s +20 m/s 0 m/s Velocity (m/s) +40 -30 -20 -10 -40 +10 +20 +30 +40 Velocity (m/s) 0 m/s -10 m/s +20 m/s 0 m/s

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) Still CV Speed up Slow down Changing velocity Object is moving fastest Moving away Moving towards

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

Graph Matching Lab 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? Final position? Displacement? Velocity at each stage? 30 25 20 15 10 5

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

Draw the PT for the following scenario: You walk to Java City for 5s You slow down as you approach the line for 5s You wait in line for 5s You turn around and speed up for 5s You 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: Still CV-AWAY 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 (-) 