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```					Chapter 11 - Forces
Section 1
Laws of Motion
p. 346
I. Newton’s First Law - Inertia

A. Inertia- tendency for an object in
motion to stay in motion and an object
at rest to stay at rest unless acted
upon by an outside force
B. Heavier objects have more inertia
Chapter 11   Section 1 Laws of Motion

Newton’s First Law
Chapter 11   Section 1 Laws of Motion

Mass and Inertia
II. Newton’s Second Law

A. Force is equal to mass times acceleration
F=ma

B. Measured in Newtons
1 Newton = 1 kg x 1 m/s2 = 1 N
Chapter 11   Section 1 Laws of Motion

Newton’s Second Law
Force Diagrams
 Force diagram – diagram showing all forces acting on
an object
Drawing a force diagram
1. Identify object you will draw a diagram for
2. Draw a dot to represent the object
3. Identify forces acting on the object (they
will be in direct contact)
4. Draw a vector to represent each force
a) In the direction of the force
b) Proportional to its magnitude
Section 2
Gravity
p. 352
Chapter 11   Section 2 Gravity

Law of Universal Gravitation
I. Universal Gravitation Equation
F= G(m1m2/d2)
A. All matter is affected by & exerts
gravity
B. Gravity increases as mass increases
C. Gravity decreases as distance
increases
II.     Free Fall and Weight
A. Free fall- when gravity is the only
force acting on an object
hammer and feather on the moon

B.      Gravitational acceleration constant
on Earth is 9.8 m/s2 = g
C.     Weight equals mass times free fall
acceleration (gravity)
1. w=mg
2. In space, you seem weightless
because everything is
accelerating (falling) at the same
rate
D. Weight and mass are different.
1. Mass is the same wherever you are
2. Weight varies according to gravity
Ex: moon = g = 1.6 m/s2

mass vs weight
E. Terminal Velocity – an object is no longer
accelerating because gravity is balanced
by air resistance
1)   when something is falling, you can calculate
the distance it fell using the formula d= ½ gt2
F. Orbital Motion – a combination of free
fall caused by gravity and forward
motion maintained by inertia
III. Projectile Motion – the curved path of an
object due to combination of 2 forces
A. forward motion creates horizontal
aspect
B. Gravity creates vertical aspect
Projectile Motion
Section 3
Newton’s Third Law
p. 360
I. Action and Reaction
A. For every action [force], there is an
equal and opposite reaction [force]
1. forces are in pairs – equal in
size but opposite in direction
2. force pairs do not act on the
same object so each object’s
motion is different
3. Equal force does not always
have equal effects
Chapter 11   Section 3 Newton’s Third Law

Action and Reaction Forces
II. Momentum
A. Momentum (p=mv) mass x velocity
p= kg x m/s (+ direction)
1. Force is related to change in
momentum over time
2. Momentum is conserved in
collisions
3. Can be transferred between
objects
a. Any momentum that is not
transferred in a collision is
conserved
B. Law of conservation of momentum
- the total amount of momentum in
an isolated system is conserved
Momentum and Collisions
Summary of Newton’s laws
Law of universal gravitation: all
objects have gravity, more mass =
more gravity; more distance = less
pull from gravity
1st law of motion: inertia
2nd law of motion: f=ma
3rd law action/reaction

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