1. Inertia! Kinematics- Study of motion of objects
How objects move
Dynamics- Study of motion of objects WITH FORCES
Why objects move
Mass- Amount of Matter that an object has
Units: Kilogram (kg)
Symbol: m
1 kg = 2.2 pounds
Inertia- a property of all matter
Tendency of object to maintain its present state of motion

2. Inertia!! What We See What Really Happens
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3. Newton's 1st Law Newton’s 1st law of motion:
Or Galileo’s law of inertia:
Whichever:
An object at rest will remain at rest,
and an object in motion will remain in motion-
at a constant speed and in a straight line,
unless acted upon by an external, unbalanced force

4. Motion Speed- The rate of distance traveled over time symbol: v units:
Velocity-
the rate of change in position( ) over time
symbol:

5. Changing Velocity OVER Acceleration- the change in velocity wrt time
Could be increase or decrease in , or turning
symbol: direction matters, so it’s a vector
units: or
OVER

6. Newton's 1st Law A Force is a push or a pull
A Force is what changes the motion of an object
Direction of the Force matters, so it is a vector quantity
Symbol:
Units: Newton (N) mass times acceleration
Kg*m/s2

7. Free Body Diagrams
A Free Body Diagram is a picture of the object, with all Forces that are acting on it.
The Forces are drawn outward from the center of the body
They can show you the Direction (and magnitude) of the TOTAL Force

8. Free Body Diagrams If you can’t draw, then just make a dot!
And draw all the forces on the object.
Label them!!! FU
FLeft
FRight wt

9. The Total Force
At any one time, an object usually has 2 forces acting on it. Think of the rope in a Tug-Of-War:
More specifically, the center of the rope
If 2 forces are going in opposite directions, then one must be thought of as positive,
and the other as negative.

10. Types of Forces
Gravity :is a force of attraction that exists between any two masses ( your mass x Acceleration of Gravity (9.8m/s2))
Friction: force resisting the relative motion of solid surfaces
Air resistance:  frictional force that acts upon objects as they travel through the air.
Applied: a force that is applied to an object by a person or another object

11. Newton's 2nd Law The acceleration that an object experiences is
directly proportional to the Total force exerted on it
That acceleration is also
inversely proportional to the mass of the object
A Total Force is what
changes the motion of an object

12. Mass and Weight are NOT the same thing!!!! Newton's 2nd Law
One of the most common forces we deal with is weight
It is the Force due to gravity
To put it into terms of Izzy’s 2nd:
The acceleration due to gravity is directly related to the Force due to gravity
and inversely related to mass (which is not due to gravity)
Mass and Weight are NOT
the same thing!!!!

13. Izzy’s 3rd Law Just to recap the first 2 Laws:
It’ll keep doing what it’s doing unless you mess with it. (Law of Inertia)
Change happens with Force
When you push on something, it’ll push back! (Action & Reaction)
Forces come in pairs

14. Izzy’s 3rd Law If you’ve ever stepped off of a rowboat onto the shore,
You step toward the shore, but the boat goes out to sea
Leaving you face down in the surf!
Picture by Paul Hewitt

15. A B Izzy’s 3rd Law Newton’s 3rd Law of Motion is this:
Given 2 objects, A & B, if A exerts a force on B, then B exerts a force on A that is equal in magnitude but in the opposite direction.
A has a mass of 100 kg
B has a mass of 70 kg B A

16. Izzy’s 3rd Law A B Draw a diagram of each object separatelyFN
Draw a diagram of each object separately
Label all forces
Circle any “3rd Law Force Pairs”
FAB A B FG
FBA FG

17. Universal Gravitation
m a
Ol’ Izzy Baby took his 3rd law o’ motion and ran with it!
This is where the legend of the apple hitting Newton on the head comes in!
If the Earth pulls the apple, then the apple pulls on the Earth.
It’s just that the Earth is SOOO much more massive than the apple that it accelerates less.
m a

18. a m 3rd Law & Jumping FE-G FG-E
When Gladys jumps, she pushes DOWN on Earth.
The Earth pushes UP on Gladys.
Equal Forces
Unequal masses
Unequal ACCELERATIONS!
Gladys a
FE-G m
Earth
FG-E m a
FG-E

19. a m 3rd Law & Walking FE-F FF-E
Foot
FE-F
FEarth-Foot a
The Foot pushes on the Earth to the right.
The Earth pushes on the Foot to the left.
Equal Forces
Unequal masses
Unequal accelerations m
FFoot-Earth
FF-E m
Earth a

20. Skydivers:
If Roy jumps out of the plane, neglecting air resistance, he will have only one force on him – Weight!

21. Skydivers: Only an idiot would jump out of plane without a parachute!
You just have to be completely nuts to jump with a parachute!
Since a parachute depends on air resistance, now we have to consider it!

22. Skydivers: At first, weight is more than the force from air resistance
After a bit of time, air resistance balances weight
If forces are balanced, velocity is constant
That’s Terminal Velocity!
Then the Parachute opens!

23. Skydivers:
Now you have the same weight, but much different surface area!
Air has more material on which to push
Crazy Roy slows down!

24. Skydivers: Eventually, Air Resistance doesn’t push as hard
Terminal Velocity occurs again, just not as much as before
Lucky for Crazy Roy, anyway!