1. Describing Motion

2. Aristotle on Force
A force is required to keep an object moving
2000 years pass….

3. Galileo 1564-1642 Lived from 1564-1642 AD
He made a big discovery that proved Aristotle was wrong
Dropped two weight objects and they both landed at the same time
So Aristotle must have been wrong about forces being necessary to keep objects moving.
Galileo said that force is required to START an object moving, but none is required to keep it moving
(when there isn’t friction)

4. Inertia Objects in motion want to stay in motion
Objects at rest want to stay at rest
Unless acted on by another force.

5. Mass and Inertia Mass is actually a measurement of inertia.
More mass = more inertia
Less mass = less inertia

6. Check it out… https://www.youtube.com/watch?v=vfnt8Sdj7cs
Inertia Demos:
Redo inertia “magic trick” with hoop and pennies/dice
Paint stick and newspaper karate chop
Hammer and bowling ball
Card and poker chips
Magic Broom
Meter vs Newton-Meter drop

7. Lesson Recap A ball rolling on a pool table slowly comes to a stop.
How would Aristotle explain this behavior?
How would Galileo explain it?
How would you explain it?

8. Speed Speed is a scalar quantity Formula: 𝑆𝑝𝑒𝑒𝑑= 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑖𝑚𝑒
Scalar means it is just a number without direction
Formula:
𝑆𝑝𝑒𝑒𝑑= 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑖𝑚𝑒

9. Velocity Velocity is a vector quantity Formula:
Vector means it has both a number AND direction
Formula:
𝑉𝑒𝑙𝑜𝑐𝑖𝑡𝑦= ∆ 𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡 ∆ 𝑡𝑖𝑚𝑒

10. Velocity Δ means “change in” which is calculated = (final – initial)
( - ) or (+) in physics just indicates direction

11. Average vs. Instantaneous
“Average” velocity is a measure of the total distance traveled in a certain period of time.
“Instantaneous” velocity is the exact speed at a specific point in time

12. Distance vs. Displacement
Distance (scalar)
Is how much ground an object has covered
Displacement (vector)
Is the overall change in position
Watch this!
Now let’s try it!
Practice Questions—write on white boards

13. Graphs
Position vs. Time graphs---
Slope = velocity value

14. Acceleration (vector)
The formula for acceleration is:
𝐴𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛= ∆ 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 ∆ 𝑡𝑖𝑚𝑒

15. Graphs
In a velocity vs. time graph
SLOPE = ACCELERATION value

16. Translations Recall that on a displacement vs. time graph
SLOPE = VELOCITY value
But what about the slope of a velocity vs. time graph?
What are the units?
Distance divided by the time squared
Example m/s2
What does the measurement mean?
It means the object is traveling fanster each second than it did in the second before

17. Summary of how to represent motion in graphs