A NICE AN EASY PROGRESSION INTO SOMETHING NEW

Change in Velocity

Position-Time Graphs

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

A: It tells you how far an object has moved during an amount of time

Best-Fit Line

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

A: It tells you the direction of motion something is moving in and the average velocity of the object

Uniform Motion

Reminder: uniform motion is when something moves equal displacements in equal time intervals

Basically it’s when something moves at a constant speed over a period of time

Uniform Motion PT Graphs

Slow, to the West Fast, to the West

Slow, to the East Fast, to the East

So…

What do you think this graph means?

Position (in m)

Hint

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

Q: What are the units of measurement for Δ v ?

A: m/s

Positive Change in Velocity

Suppose you are riding a bicycle travelling forwards at 6 m/s. You need to get somewhere in a hurry, so you increase your velocity to 9 m/s forward. What is your change in velocity?

Negative Change in Velocity

Suppose you are riding your bicycle and you apply the breaks to slow down. If you slow down from 9 m/s forward to 2 m/s forward, what is your change in velocity?

Practice Examples

You are walking to school at 0.5 m/s and realize you are late, so you speed up to 0.8 m/s. What is your change in velocity?

You are biking down a trail at 5.2 m/s and you encounter a large fallen tree, so you come to a stop to hop over it. What is your change in velocity?

Practice Examples

You are going for a jog at 3.4 m/s and get attacked by zombies, so you speed up to a sprint away at 8.3 m/s. What is your change in velocity?

You are driving down the street at 55 km/h and you notice a sale advertisement in the window of your favorite store. You slow down to 37 km/h to give yourself enough time to read the details. What is your change in velocity?