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 Motion1. 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)

26,400 mph

Earth to solar escape 36,500 mph

Rockets deal with Newton’s 3rd law of motion…

Work Cited

• “Sonic Boom Plane”. April 7, 2008. http://www.aviationexplorer.com/sonicboomplane_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/docs/Propulsion/2-how-fast-conventional.html