Download The First Law of Motion

NOTES – UNIT 3: MOTION & NEWTON’S LAWS
CHAPTER 4– The Laws of Motion
I.
The First Two Laws of Motion
A. Newton’s Laws
- Sir Isaac Newton (1642–1727) able to state rules that describe the
________________ of ____________ on the motion of objects
B. The First Law of Motion
***An object moving at a constant velocity keeps moving at that velocity unless
an unbalanced net force acts on it (LAW OF INERTIA)***
C. Inertia & Mass
--inertia-- the tendency of an object to resist any change in its motion
- If object is moving  it wants to ______________ _________________
- If object is at rest  it wants to ______________ at ______________
UNLESS….
…_________________ forces act on it!
-The _____________ of an object remains ________________…
UNLESS…
… a force ______________________ it!
-The ________________ of an object is related to its _______________
-The _________________ the mass of an objectthe _____________ its inertia
-- mass -- the amount of matter an object has
-- weight -- the amount of mass PLUS the force of gravity acting on an
object
-Force is calculated using units of _____________ AND ___________ (or g) 
these units combine into a unit called a _______________ (mass + acceleration)
D. The Second Law of Motion
***The acceleration of an object is in the same direction as the net force on the
object ***
1.) Force & Acceleration
-Acceleration can be calculated from the following equation:
Force = mass x acceleration
Mass = Force / acceleration
Acceleration = Force / Mass
REMEMBER: acceleration is the change in velocity divided by the time it takes for
the change to occur 
HINT: Now for problems you may have to solve for
acceleration first before dividing the force!!!
2.) Mass & Acceleration
-The acceleration of an object _____________ on its ____________ as well as the
____________ exerted on it
- MASS vs. WEIGHT:
 An object will always have the same MASS (amount of matter) no matter
where that object is….Translation: __________ STAYS THE ____________!
 An object’s WEIGHT (mass + force of gravity) may be different in
different places in the universe because of different forces of
gravity…Translation: _______________ CAN _________________!
II.
Gravity
A. What is Gravity?
-- gravity -- attractive force between any 2 objects
 depends on the _________________ of the objects & the
___________________ between them
-Increasing mass increases an objects gravitational force!
- Decreasing distance between objects increases gravitational force!
1.) Gravity – A Basic Force
-The “Big 4” Forces:
_________________________
_________________________ Force
_________________________ Force
_________________________ Force
B. Law of Universal Gravitation
_______  universal gravitational constant
_______  distance between two masses
____&_____  the two masses
TRANSLATION:  Law of Universal Gravitation enables the force of
_____________ to be calculated between any 2 objects if their
____________ & the ______________ between them is ______________
1.) Range of Gravity
- No matter how far apart 2 objects are, the gravitational force between them
______________ completely goes to __________
 Gravity is a __________--_____________ FORCE
C. Earth’s Gravitational Acceleration
- When all forces except gravity acting on a falling object can be ignored, the
object is said to be in ____________ __________
-Close to Earth’s _______________, the acceleration of a falling object in free fall
is about ___________
- Symbol for acceleration of gravity  ____
-By Newton’s 2nd law of motion force of Earth’s gravity on a falling object =
object’s mass times the acceleration of gravity… ____ = _____
x _____
UNIT USED = _________________ (N)
1.) Weight
W=m x g
(Weight = mass x gravitational constant – 9.8 m/s²)
***Weight is a ______________ ***
***Mass is a measure of the amount of _______________ an object contains***
D. Weightlessness & Free Fall
- If gravitational forces never disappear  how does one become
“__________________” (example: astronauts in space)?
-Objects will seem to float because they are all ________________ with the
_____________ __________________  astronaut & ship are falling towards
Earth but falling at the SAME _________________
E. Projectile Motion
- Earth’s gravity causes projectiles to follow a ____________ ____________
1.) Horizontal & Vertical Motion
-When you throw a ball force exerted ____________ the ball
________________ to give it HORIZONTAL MOTION
-Horizontal Velocity of ball is _____________ (*ignoring air resistance*)
-When you let go of the ball, _____________ pulls it _______________ giving it
VERTICAL MOTION  ball travels in a curve
2.) Horizontal & Vertical Distance
-If a ball as thrown in a perfectly horizontal direction, would it take longer to
reach the ground than a dropped a ball from the same height?
-_________!!! They would drop at the same time!
-Both balls travel the _____________ ________________ distance in the same
amount of time  thrown ball travels a ______________
__________________ distance
F. Centripetal Force
- When a ball enters a curve it is accelerating because its _____________ is
_________________ (even if its speed does not change)
-When a ball goes around a curve change in the direction of the velocity is
_____________ the _______________ of the curve
--centripetal acceleration-- acceleration toward the center of a curved or
circular path
--centripetal force-- net force exerted toward the center of a curved path
1.) Centripetal Force & Traction
-A car rounds a curve on a highway ______________ force acts on the car to
keep it moving in a ____________ path
 Centripetal Force is the ____________ force (traction) between the
____________ & ___________ surface
III.
Newton’s Third Law
-When one object exerts a force on a second object the second one exerts a
force on the first that is equal in strength & opposite in direction
A. Action & Reaction
- When a force is applied in nature a ________________ force occurs at the
___________ __________
-Even though the forces are equal, they are _________ ____________ because
they act on ___________________ ________________
EXAMPLE: A swimmer “acts” on the water, the “reaction” of the water
pushes the swimmer forward
 a net force, or unbalanced force, acts on the swimmer so a change in
their motion occurs
B. Momentum
--momentum-- a product of mass & velocity
- Momentum symbol  _______
- Unit for momentum _______
1.) Force & Changing Momentum
-By combining ____________________ equation & ____________ equation
Newton’s 2nd Law Equation:
***_____________ Momentum  mvf
***_____________ Momentum  mvi
C. Law of Conservation of Momentum
-__________________ of an object doesn’t change….
…UNLESS
…its ____________, _______________, or both
change!
-Momentum can be ___________________from one object to another!
Law of Conservation of Momentum: If a group of objects exerts forces only
on each other their total momentum doesn’t change
1.) When Objects Collide
- Results of a collision depend on the momentum of ____________
________________
- When an object hits another from behind  momentum occurs in the
______________ direction
- When an object hits another head on with the same force  momentum is
__________
- If one object hits another head on with the more/less force  momentum is
_______________________