Change in VelocityA nice an easy progression into something new

Position-Time Graphs

Q: What does a position-time graph tell you/show you?

A: (write down what you think it is)

It tells you how far something has moved and how long it took to move

It tells you the average velocity of that movement

Best-Fit Line

Q: What does the line on a position-time graph tell you?

A: (write down what you think it is)

It tells you the direction of motion something is moving in

It shows you the average velocity of something

Positive Direction Graph

Time (s) Position (m)

0 0

2.2 5

4.5 10

6.7 15

9.0 20

1. Label time (s) along the bottom

2. Label position (m) along the left side

3. Make your scale4. Plot your points5. Draw a best-fit line6. Pick 2 points on the line

(not 0,0 and not points that are data points)

7. Indicate which point is your initial and which point in your final

8. Use those two points to find the slope’s velocity

Negative Direction Graph

Time (s) Position (m)

0 20

3.9 15

8.1 10

12.0 5

15.8 0

1. Label time (s) along the bottom

2. Label position (m) along the left side

3. Make your scale4. Plot your points5. Draw a best-fit line6. Pick 2 points on the line

(not 0,0 and not points that are data points)

7. Indicate which point is your initial and which point in your final

8. Use those two points to find the slope’s velocity

Motion Investigation Activity

Think about motion

Q: Why do you think it took less time to roll from 35.5cm – 71cm then it did from 0cm – 35.5cm?

A: (write down your thoughts)

  

Notes: 

The marble did not roll down the ramp at a constant velocity

The marble’s velocity changed over time

Change in Velocity

A change in velocity occurs when the speed of an object changes, or its direction of motion changes, or both

Change in Velocity

Q: What do you think the symbol for a change in velocity is?

A: Δ v (remember Δ is the Greek symbol delta meaning a change)

Q: How do you think you find the change in velocity (Δ v)?

A: Δ v = vf - vi