Chapter 8 Notes
Motion and Forces
Chapter 8.1 Notes
• Speed: distance traveled divided by the
time interval during which the motion
occurred
Speed=Distance/time
• Constant speed: speed does not change
• Velocity: is a quantity describing both
speed and direction (same number as
speed but with a direction added)
• Momentum: a quantity defined as the
product of an objects mass and its velocity
Momentum = Mass x Velocity
Chapter 8.2 Notes
• Acceleration change in velocity, if the
object speeds up, slows down, changes
direction.
Acceleration =
Final velocity - initial velocity
time
• Force the cause of acceleration, or change
in an object’s velocity.
• Balanced forces are forces acting on an
object that combine to produce a net force
equal to ZERO.
• Unbalanced forces are forces acting on an
object that combine to produce a net
nonzero force.
• Friction the force between two objects that
opposes the motion of either object. So
whenever two objects touch there is
friction.
• Air resistance is a type of friction.
• Low friction shoes on ICE
• High friction shoes on pavement
• Gravity- the attraction between two
particles of matter due to their mass.
• The larger the mass the larger the
gravitational pull.
• The closer together the two objects are the
greater the gravitational pull.
Chapter 8.3 Notes
Newton’s 3 Laws of Motion
1. An object at rest remains at rest and an
object in motion maintains its velocity
unless it experiences an unbalanced
force.
2. The unbalanced force action on an
object equals the object’s mass times its
acceleration. Force= (m)(a)
3. For every action force, there is an equal
and opposite reaction force.
Newton’s 1st law
• Inertia the tendency of an object to remain at
rest or in motion with a constant velocity.
• That is why we wear seatbelts, put babies in
car seats, need to sit away from airbags.
New York State passed the first seat belt law
in the US in 1984 under the leadership of
John D. States, an orthopedic surgeon who
dedicated his career to improving automotive
safety.
• Remember, it is not just the law, but a way to help
prevent accidental injury or death when your children are
riding in a vehicle. These laws are the minimum
requirements. Children are safer riding in booster seats
through 80 pounds than using the vehicle's seats and
restraint systems designed for adults.
Many states are seeking to change their laws to
require children stay in restraints through 8 years and 80
pounds.
Newton’s 2nd law
• Free fall is when the force of gravity is the
only force action on an object.
• Gravity (g) = 9.8 m/s2
• Weight = mass times gravity
• Terminal velocity is the maximum velocity
reached by a falling object.
• Weight is the pull of gravity on an
object…changes from place to place.
• Mass is the amount of matter in an
object…NEVER changes.
How Fast do Rockets Go??
Flight Plan
Speed Required
Earth to LEO (low Earth orbit)
17,000 mph
Earth to Earth escape
24,200 mph
Earth to lunar orbit
25,700 mph
Earth to GEO (geosynchronous
Earth orbit)
Earth to solar escape
26,400 mph
Rockets deal with Newton’s 3rd law of motion…
36,500 mph
Work Cited
• “Sonic Boom Plane”. April 7, 2008.
http://www.aviationexplorer.com/sonicboomplan
e_navy.jpg
• “US map of car seat law and info”. April 9, 2008.
http://www.inventiveparent.com/state-laws.htm
• “Seat belt laws”. April 9, 2008.
http://en.wikipedia.org/wiki/Seat_belt_legislation
• “rocket info.” April 9, 2008.
http://www.qrg.northwestern.edu/projects/vss/do
cs/Propulsion/2-how-fast-conventional.html