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Chapter 10
Section 1 –
The Nature of Force
 Force
- a push or pull
 Like
velocity and acceleration, a force is
described by its strength and by the
direction in which it acts.
 SI unit Newton
 The combination of all forces acting on
an object is called the net force.
Chapter 10
Section 1 –
The Nature of Force
Unbalanced Forces - acting on an object will
change the object’s motion
 Unbalanced forces acting on an object result
in a net force and cause a change in the
object’s motion.
 Equal forces acting on one object in opposite
directions are called balanced forces.
 Balanced Forces - acting on an object will not
change the object’s motion

Chapter 10
Section 2 –
Friction and Gravity
 Friction
- The force that two surfaces
exerts on each other when they rub
against each other.
 The
strength of the force of friction
depends on two factors: how hard the
surfaces push together and the types of
surfaces involved.
Chapter 10
Section 2 – Friction (cont.)

Types of friction
– Static Friction – Friction that acts on objects that
are not moving
– sliding friction - objects slide against each other
– rolling friction - object is round or has wheels
– fluid friction - object moves through fluid
(swimming)
Is friction bad?
 ice, walking, car, bike

Chapter 10
Section 2 – Gravity
The force that pulls objects toward Earth
 Law of Universal Gravitation - The force of
gravity acts between all objects in the
universe.
 Too factors affect the gravitational attraction
between objects: mass and distance.
 Mass - measure of the amount of matter in an
object
 Inverse relationship between distance
between object and their gravitaional pull

Chapter 10
Section 2 – Gravity (cont.)
Weight - measure of the force of gravity on an
object
 Earth vs. Moon
 Weight (Newtons) = mass x 9.8m/sec2

Chapter 10
Section 2 - Gravity (cont.)
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Free fall - only gravity acting on the object (in a
vacuum)
In free fall, the force of gravity is an unbalnced force,
which causes an object to accelerate.
Acceleration due to Gravity = 9.8 m/s2
Air Resistance - Objects falling through the air
experience a type of fluid friction
 Terminal velocity – The greatest velocity a
falling object reaches


air resistance forces balanced with gravity
Section 2 – Gravity (cont.)
Projectile – An object that is thrown
 Projectile motion –throw object horizontally
(football, soccer)

Chapter 10
Section 3 –
Newton’s First & Second Laws
Newton’s First Law of Motion
An object at rest will remain at rest, and
an object that is moving at a constant
velocity will continue moving at constant
velocity, unless it is acted upon by an
unbalanced force.
Chapter 10
Section 3 –
Newton’s First Law
 Inertia
- the tendency of an object to
resist a change in it’s motion
 Direct relationship between mass and
inertia.
(One can say that mass is a measure of
an objects inertia.)
Chapter 10
Section 3 –
Newton’s Second Law
Newton’s Second Law of Motion
The acceleration of an object is directly
proportional to force and inversely
proportional to mass.
Acceleration = Net Force/Mass
Force = Mass x Acceleration
Chapter 10
F=ma
Section 3 –
Newton’s Second Law
 Mass
- the amount of matter in an
object
(SI units = kilogram (kg))
 Force = Newtons (N),
Mass=kilograms (kg), Acceleration =
m/sec2
 Sample Problems pg.351
Chapter 10
Section 4 –
Newton’s Third Law (cont.)

Newton’s Third Law of Motion
If one object exerts a force on another object,
then the second object exerts a force of equal
strength in the opposite direction on the first
object.
Chapter 10
Section 4 –
Newton’s Third Law (cont.)
– pg. 354 Gymnast,
kayaker, dog (Squid, skater, kick,
walking)
 Action Reaction Pairs
 Motion?
 Forces cancel? Volleyball pg.355
 Action-Reaction
Chapter 10
Section 4 –
Momentum
Newton called momentum an objects quantity
of motion
 The momentum of a moving object can be
determined by multiplying the object’s mass
and velocity.
 Momentum = mass x velocity

– Sample problems pg.356
Chapter 10
Section 4 –
Momentum (cont.)
 Law
of Conservation of Momentum
The total momentum of any group of
objects remains the same (is
conserved), unless outside forces act
on the objects.
 Train
examples - overheads pg.358
Chapter 10
Section 5 –
Orbiting Satellites
lift off - Newton’s third law gasses expelled with a downward force,
exert an equal but opposite force
upward on the rocket.
 Satellite - any object that orbits another
object in space
 centripetal force - any force that causes
an object to move in a circular path
 Rocket
Chapter 10
Section 5 –
Orbiting Satellites (cont.)
 satellites
in orbit around the Earth
continually fall toward Earth, but
because Earth is curved they travel
around it pg.364
 Satellite Motion
 Satellite location – LEO,
Geo Synchronous
Chapter 10
Chapter 10 Vocabulary
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force
net force
inertia
Newton’s first law
Newton’s second law
Newton’s third law
Friction
Static Friction
Sliding Friction
Rolling Friction
Fluid Friction
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gravity
Mass
Weight
Free fall
Air resistance
Terminal velocity
Projectile
momentum
conservation of
momentum
satellite
centripetal force
Chapter 10