Physics 9/22

Welcome back to class everyone!

So there's some stuff I need to go over to make last week's assignment make more sense.

Poll

Before we start, how are you feeling today?

Last time we did some graphing!

Well, you should have. Based on that tumble buggy video you should have created a graph using google sheets...

Multiple Choice

What kind of graph did we make it last time??

• Position vs Time Graph

• Speed vs Time Graph

• Velocity vs Time Graph

• Time vs Time Graph

Let's talk about graphs!

specifically PvT graphs

Position

Position describes the location of an object in space relative to some reference point or system. (GPS coordinates for example)

In the lab we tracked the changes in the buggy's position over time.

PvT Graph

When you plot the changes in position over time.

You get what we refer to as a Position vs Time graph.

Or PvT graph.

Velocity

When you calculate the slope (rise/run) of a PvT graph you get velocity!

Velocity is the speed and direction of an object.

Open Ended

If the slope of a PvT graph equals Velocity. Then what do you suppose the formula for Velocity is??

(hint = think of the formula to calculate slope and how it relates to a PvT graph.)

Displacement

Displacement is the change in an object's position.

So we can also refer to a Position vs Time graph as a Displacement vs Time graph!

For instance:

In the PvT graph to the right you can see the changes in the object's position.

You will find the object's displacement by taking the difference between any 2 positions.

Multiple Choice

Given what you know about displacement now. Which of the following do you think is the Velocity equation?

• $v\ =pt$

• $v=\frac{d}{t}$

• $v=dt$

• $v=\frac{t}{d}$

Additional things to know about PvT graphs

You can determine if the object is moving in a positive direction or negative direction based on the slope direction. Up is positive, down is negative.

A flat line on a PvT graph means that the object is not moving. Velocity is 0!

Multiple Choice

Which of the following graphs shows an object at rest (or not moving)?

Multiple Choice

Which of the following graphs an object moving with constant positive velocity?

Multiple Choice

Which of the following graphs shows an object moving with constant negative velocity?

Open Ended

What do you suppose is happening to the velocity in this graph? Can you think of a term that would describe it?

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